Unit Three: Waves

1) A wave traveling in water has a frequency of 250 Hz and a wavelength of 6.0 m. What is the speed of the wave? 2) The lowest-pitched sounds humans can generally hear have a frequency of roughly 20 Hz. What is the approximate wavelength of these sound waves if their wave speed is 340 m/s? 3) A particular radio station broadcasts radio waves at 100 MHz (100 million Hz). If radio waves travel at the speed of light (300 million m/s), then what is the wavelength of the radio waves that the station is broadcasting? 4) Challenge A sound wave with a frequency of 100.0 Hz travels in water with a speed of 1,500 m/s and then travels in air with a speed of 340 m/s. Approximately how many times larger is the wavelength in water than in air?

1) 2) 3) 4)

7) Compare and contrast the properties and uses of radio waves, infrared waves, and ultraviolet rays. 8. Explain A mug of tea is heated in a microwave oven. Explain why the tea gets hotter than the mug. 9. Identify the beneficial effects and the harmful effects of human exposure to ultraviolet rays. 10. Name three objects in a home that produce electromagnetic waves, and describe how the electromagnetic waves are used. 11. Think Critically How could infrared imaging be used to find a lost hiker?

7) All are electromagnetic waves; radio waves are very long & are used for communications; Infrared waves are long and are used for thermal imaging; Ultraviolet waves are short and are used for purification & forensic 8) water (tea) absorbs more energy (microwaves) than ceramics (mug) so it gets hotter 9) Beneficial - Purification & vitamin D production; Harmful - damage proteins, DNA molecules, skin, & cause cancer. 10) remote controls use infrared rays; microwaves cook our food; Lights give us light 11) When you scan the area the hiker's body would appear as a warm dot, unless dead.

Rainbows

Does the light leaving the prism in Figure 5 remind you of a rainbow? Like prisms, rain droplets also refract light. The refraction of the different wavelengths can cause white light from the Sun to separate into the individual colors of visible light, as shown in Figure 6. In a rainbow, the human eye can usually distinguish only about seven colors clearly. In order of decreasing wavelength, these colors are red, orange, yellow, green, blue, indigo, and violet.

What is the Carrier Wave

Each radio station is assigned a particular radio frequency for their broad casts- this specific frequency is a carrier wave

Radio Transmissions

Each radio station uses an assigned frequency to avoid interfering with other radio broadcasts. Television stations and cell phone companies are also assigned specific frequencies. These frequency ranges are shown in Figure 18. The remaining radio frequencies are assigned for other purposes, such as navigation and radio astronomy. Changing the channel on your radio or television allows you to select a particular frequency carrying the information you want to listen to or watch. An electromagnetic wave with the specific frequency that a station is assigned is called a carrier wave. Modulation The station must do more than simply transmit a carrier wave. It must also send information about the sounds that you are to receive. The sounds produced at the radio station are converted into electric signals. This electric signal is called the signal wave and is used to modify the carrier wave. The process of adding the signal wave to the carrier wave is called modulation. There are two ways to modulate carrier waves: amplitude modulation (AM) and frequency modulation (FM). AM radio An AM radio station broadcasts information by varying the amplitude of the carrier wave, as shown at the left in Figure 19. AM carrier wave frequencies range from 540,000 to 1,600,000 Hz. FM radio In FM radio signals, the signal wave is used to vary the frequency of the carrier wave, as shown at the right in Figure 19. Because the strength of the FM waves is kept fixed, FM signals tend to be more clear than AM signals. FM carrier frequencies range from 88 million to 108 million Hz. These frequencies are much higher than AM frequencies.

Incandescent Lights

Many of the lightbulbs in your house probably produce incandescent light. Incandescent light is light generated by heating a piece of metal until it glows. Inside an incandescent lightbulb is a small wire coil, called a filament, that usually is made of tungsten metal. When there is an electric current in the filament, the electric resistance of the metal causes the filament to become hot enough to give off light. However, about 90 percent of the energy given off by an incandescent bulb is in the form of thermal energy

Longitudinal Wave

Matter in the medium moves back and forth along the same direction that the wave travels. Imagin e acoled spring toy. Squeeze several cols together at one end of the spring. Then let go of the coils, still holding onto cols at both ends of the spring. A wave will travel along the spring. It looks as if the whole spring is moving toward one end.

Medium

Matter through which a wave travels

Receiving radio waves

As electromagnetic waves pass by your radio's antenna, the electrons in the metal vibrate, as illustrated in Figure 21. These vibrating electrons produce a changing electric current that contains the information about the music and words. This current is used to make the speakers vibrate, creating the sound waves that you hear.

Ultrasound

High frequency sound waves ( Ex: medicine, pregnancy, breaking up kidney stones.)

Electric and magnetic fields

Recall that electric charges are surrounded by electric fields and that magnets are surrounded by magnetic fields. These fields exert a force even when the charge or magnet is not in contact with an object. Fields exist around an electric charge or a magnet even in a vacuum. A vacuum is a volume of space that contains little or no matter. You might also recall that a moving electric charge, such as the current in the wire shown in Figure 2, is surrounded by a magnetic field. Similarly, a moving magnet is surrounded by an electric field. A changing electric field creates a magnetic field, and a changing magnetic field creates an electric field.

Sound Waves

Recall that air is composed of matter. When an object such as a radio speaker vibrates, it collides with some of the particles that make up the nearby air, transferring some energy to those particles. These particles then collide with other particles, passing the energy on farther. The energy originally transferred by the vibrating object continues to travel through the air in this way. This process of energy transfer forms a sound wave. Sound waves are longitudinal waves. Remember that a longitudinal wave is composed of two types of regions called compressions and rarefactions. If you look at Figure 1, you will see that when a radio speaker vibrates outward, the particles near the speaker are pushed together, forming a compression. When the speaker moves inward, the particles near the speaker are spread apart, and a rarefaction forms. As long as the speaker continues to vibrate back and forth, sound waves are produced.

Intensity and Loudness

Recall that the degree of disturbance from a wave corresponds to its amplitude. For a longitudinal wave, amplitude is related to how close the particles of the medium are together in the compressions. Figure 6 compares longitudinal waves of low amplitude and high amplitude. Increasing the amplitude of a longitudinal wave pushes the particles in that wave's compressions closer together. To produce a sound wave with greater amplitude, more energy must be transferred from the vibrating object to the medium. This greater energy is then transferred through the medium as the sound wave is transmitted. What happens to the sound waves from your stereo when you adjust the volume? The notes sound the same, but you decreased the amplitude of the sound waves. For sound waves, the amplitude of the wave is related to its intensity

Holography

Science museums often have exhibits where a three dimensional image seems to float in space, like the one shown in Figure 21. You can see the image from different angles, just as you would if you viewed the real object. These images are produced by holography. Holography is a technique that produces a hologram, a complete three-dimensional photographic image of an object. The three-dimensional images on some credit cards are also produced by holography. Making holograms Lasers are needed to produce holograms. The laser beam is split into two parts. One part illuminates the object and reflects onto photographic film. At the same time, the second part of the beam is also directed at the film. The light from the two beams creates an interference pattern on the film. The pattern looks nothing like the original object, but when laser light shines on the pattern on the film, a holographic image is produced.

Communications Satellites

Since satellites were first developed, thousands have been launched into Earth's orbit. Many of these, like the one in Figure 25, are used for communication. The sender broadcasts a microwave signal to the satellite. The satellite receives the signal, amplifies it, and transmits it to a particular region on Earth. Like cell phones, satellites are transceivers. To avoid interference, the satellite receives signals at one frequency and broadcasts signals at a different frequency. Satellite telephone systems Some mobile telephones can be used when sailing across the ocean, even though there are no nearby cell phone towers. The telephone transmits the signal directly to a satellite. The satellite relays the signal to a ground station, and the call is passed on to the telephone network. Satellite links work well for one-way transmissions, but two-way communications can have a delay caused by the large distance the signals travel to and from the satellite. Television satellites The satellite-reception dishes that you sometimes see in yards or attached to houses are receivers for television satellite signals. Satellite television is used as an alternative to ground-based transmission. Communications satellites use microwaves rather than the radio waves used for normal television broadcasts. Microwaves have shorter wavelengths and travel more easily through the atmosphere. The ground receivers are dish-shaped to help focus the microwaves onto an antenna.

Mirror

Smooth surface that reflect to form images

Using total internal reflection

Total internal reflection makes light transmission in optical fibers possible. As shown in Figure 23, light entering one end of the fiber is reflected continuously from the sides of the fiber until it emerges from the other end. The light moves like water through a pipe—almost no light is lost or absorbed in optical fibers. The core of the fiber and the surrounding layer are made from glasses with two different indexes of refraction. Light moves more slowly in the core than in the surrounding layer. Therefore, total internal reflection can occur at the surface between the two layers.

Ultraviolet Waves

Ultraviolet waves are electromagnetic waves with wavelengths from about 400-billionths to 10-billionths of a meter. Ultraviolet waves (UV waves) can enter cells, making ultraviolet waves both useful and harmful. Useful UVs You probably know that UV waves cause sunburn. But some exposure to ultraviolet waves is healthy. Ultraviolet waves striking the skin enable your body to make vitamin D, which is needed for healthy bones and teeth. Ultraviolet waves are also used to disinfect food, water, and medical supplies, as shown in Figure 13. When ultraviolet light enters a cell, it damages protein and DNA. For some single celled organisms, such as bacteria, this damage can mean death. Ultraviolet waves make some materials fluoresce (floo RES). Materials that fluoresce absorb ultraviolet waves and reemit the energy as visible light. Police detectives sometimes use fluorescent powder to reveal fingerprints. Harmful UVs When you spend time in the Sun, you might wear sunscreen to prevent sunburn. Most of the UV waves that reach Earth's surface are longer-wavelength UVA rays. The shorter-wavelength UVB rays are the primary cause of sunburn and skin cancers, but UVA rays contribute to skin cancers and skin damage, such as wrinkling. The ozone layer About 20 to 50 km above Earth's surface is a region called the ozone layer. Ozone is a molecule composed of three oxygen atoms. The ozone layer is vital to life on Earth because it absorbs most of the Sun's harmful ultraviolet waves and prevents them from reaching Earth's surface, as shown in Figure 14.

The Digital Revolution

Until the early 21st century, information was sent to TV sets in the same way it was sent to radios. The audio information was sent using FM, and the visual information was sent using AM. The information signals were analog signals. Analog signals are electric signals whose values change smoothly over time. In 2009, full-power television stations in theUnited States began broadcasting only digital signals. A digital signal is an electric signal where there are only two possible values: ON and OFF. This is similar to a light switch where the light can be on or off, but it cannot be half-on or half-off. There are many ways to modulate radio waves using this on-and-off information. The simplest methods, however, resemble traditional AM and FM and are called Amplitude-Shift Keying (ASK) and Frequency-Shift Keying (FSK). These types of digital modulation are shown in Figure 22. More complex ways of digital modulation allow more information to be carried by a single wave. In the United States, television stations use multiple amplitude modulations to encode data on the carrier wave.

1. MAIN Idea Infer Would a vibrating proton produce an electromagnetic wave? Would a vibrating neutron? Explain. 2. Compare the frequency of an electromagnetic wave with the frequency of the vibrating charge that produces the wave. 3. Describe how electromagnetic waves transfer energy to matter. 4. Explain how an electromagnetic wave can travel through space that contains no matter. 5. Think Critically Would a stationary electron produce an electromagnetic wave? Would a stationary magnet? Explain.

1) Proton yes, because it is a charged particle; Neutron no, because it is not a charge particle 2) They are equal 3) by causing charged particles within objects to move 4) An electromagnetic wave is made of vibrating electric and magnetic fields that continually induce each other; matter is not needed for this to occur. 5) No; No; they have to move to produce a wave.

1. MAIN Idea Describe the motion of an unanchored rowboat when a water wave passes. Does the wave move the boat forward? 2. Contrast how you would move a spring to make a transverse wave with how you would move a spring to make a longitudinal wave. 3. Identify evidence that seismic waves transfer energy without transferring matter. 4. Identify a mechanical wave that is also a longitudinal wave. 5. Think Critically Describe how the world would be different if all waves were mechanical waves. 6. Calculate Time The average speed of sound in water is 1,500 m/s. How long would it take a sound wave to travel 9,000 m in water?

1) The boat will move up and down because of the waves but it will not move forward because the wave doesn't carry the boat with it 2) To make the transverse wave, I would have one person hold one end of the spring and on the other end I would move it up and down. To make the longitudinal wave, I would squeeze the coils together at one end and then let go of them while still holding onto the coils at the end 3) Seismic waves and cause great change. Tidal waves and direct damage to building and other structures are caused by earthquakes. However, the waves move through Rock and soil. Rock and soil are not carried along with the waves. 4) Sound 5) If all waves were mechanical waves then light waves would not be able to travel through the vacuum of space. The energy from the Sun would have no way to reach the Earth. As a result, Earth would be very cold and dark. 6) t = d/s t = 9,000/1,500 t = 6 seconds

1. MAIN Idea Explain how sound travels from your vocal cords to your friend's ears when you talk. 2. Summarize the physical reasons that sound waves travel at different speeds through different mediums. 3. Explain why sound speeds up when temperature increases. 4. Describe each section of the human ear and its role in hearing. 5. Think Critically Some people hear ringing in their ears, called tinnitus, even in the absence of sound. Form a hypothesis to explain why this occurs.

1) Your vocal cords vibrate and then travel through the air to your friends ear. 2) different temperatures, density, and elasticity change the speed of sound waves 3) particles increase in speed when temperature increases 4) The purpose of the outer ear is to Gather energy in the form of sound waves. The purpose of the inner ear is to Covert sound vibrations to electrical impulses The purpose of the middle ear is to Amplify vibrations from sound waves and transfer them to the cochlea. 5) Well, when the ear cells die, like any other kind of life, energy is dissipated . So since so many ear cells are needed to hear, the many that die at once give off the energy as an audible energy.

1. MAIN Idea Describe two ways that you could direct a light wave around a corner. 2. Predict how rubbing a mirror with sandpaper will affect how the mirror reflects light. 3. Identify what an object's index of refraction indicates. 4. Explain what happens to white light when it passes through a prism. 5. Think Critically Decide whether the lens of your eye, your fingernails, your skin, and your tooth are opaque, translucent, or transparent. Explain. 6) Find an Angle A light ray strikes a mirror at an angle of 42° from the surface of the mirror. What angle does the reflected ray make with the normal? 7. Find an Angle A ray of light hits a mirror at 27° from the normal. What is the angle between the reflected ray and the normal?

1) use mirrors to change light direction, use glass, plastic or other clear substances to refract light around a corner 2) It would make the surface rougher so it would produce a diffuse reflection. 3) it indicates how much light will slow down in the material compared to its speed in a vacuum 4) the white light get refracted at different amounts because of its wavelength and get separated into a rainbow 5) lens is transparent because light passes through without scattering. Fingernails and skin are translucent because light passes through them but you cannot see through them. Teeth are opaque because light doesn't pass through them. 6) 48° 7) 27

11. MAIN Idea Identify a wave that speeds up when it passes from air to water as well as one that slows down. 12. Describe the difference between a longitudinal wave with a large amplitude and one with a small amplitude. 13. Describe how the wavelength of a wave changes if the wave slows down but its frequency does not change. 14. Explain how the frequency of a wave changes when the period of the wave increases. 15. Think Critically You make a transverse wave by shaking the end of a long rope up and down. Explain how you would shake the end of the rope to make the wavelength shorter. 16. Calculate the frequency of a water wave that has a wavelength of 0.5 m and a speed of 4 m/s. 17. Calculate Speed An FM radio station broadcasts radio waves with a frequency of 96,000,000 Hz. What is the speed of these radio waves if they have a wavelength of 3.1 m?

11) A sound wave speeds up as it passes from air to water. A light wave slows down as it passes from air to water. 12) Large Amplitude = More energy Small Amplitude = Less energy 13) If the wave slows down with no change in frequency, the wavelength decreases. 14) The frequency of a wave decreases when the period of the wave increases. 15) To make the wavelength shorter, you would increase the frequency of shakes. 16) Speed = (wavelength)(frequency) Speed = (3.1)(96,000,000) Speed = 297,600,000m/s

14. MAIN Idea Identify and describe the steps that a radio station uses to broadcast sounds to your radio receiver . 15. Explain the difference between AM and FM radio. Make a sketch of how a carrier wave is modulated in AM and FM radio signals. 16. Describe what happens to your signal when you are talking on a cell phone and you travel from one cell to another cell. 17. Explain some of the uses of the Global Positioning System. Why might emergency vehicles be equipped with GPS receivers? 18. Think Critically Why do cordless telephones stop working when you move too far from the base unit?

14) Sound is converted into a signal. signal causes electrons in antenna to vibrate. Vibrating electrons produce electromagnetic (EM) wave. EM wave causes electrons in your antenna to vibrate. Radio turn vibrating electrons into sound. 15) AM radio modulates amplitude. FM radio modulates frequency 16) A central controller transfers your signal to the base station in the new cell. 17) GPS is used by hikers, airplanes, ships, cars, and others to identify their location on Earth. Emergency vehicles have GPS to help them find places quickly. 18) The signal decreases with distance and the signal becomes too weak.

15. MAIN Idea Compare and contrast the two main types of bulbs found in your home. Explain how they produce light. 16. Discuss the advantages of using a fluorescent bulb instead of an incandescent bulb. 17. Describe the difference between coherent and incoherent light. 18. Describe the processes used to produce light in a laser. 19. Identify several uses of lasers. 20. Think Critically Which type of lighting device would you use for each of the following needs: an economical light source in a manufacturing plant, an eye-catching sign that will be visible at night, and a baseball stadium? Explain. 21. Calculate Efficiency A 25-W fluorescent light emits 5.0 J of thermal energy each second. What is the efficiency of the fluorescent light? 22. Use Percentages If 90 percent of the energy emitted by an incandescent bulb is thermal energy, how much thermal energy is emitted by a 60-W bulb each second?

15) incandescent: heats a tungsten filament until it glows fluorescent: electrons collide with gas atoms, UV light is emitted, the phosphors convert UV light to visible light 16) fluorescent bulbs last longer and waste less energy 17) coherent light: one wavelength; one direction; constant distant between crests incoherent light: many wavelengths, many directions, varying distance between crests 18) Atoms in the laser tube absorb light from a flash tube and emit light at one wavelength. Some light waves are reflected between two mirrors and cause more atoms to emit light, resulting in a narrow, intense light beam. 19) read CDs, surgery, light shows, pointers 20) Eradiant = Ein - Ethermal Efficiency = Eout/Ein The correct answer is: 80% 21) 54 J

MAIN Idea Compare and contrast music and noise. 15. Explain how two instruments could be used to produce a pulsing sound, and identify the name for this pulsing sound. 16. Explain how a flute, a violin, and a kettledrum each produce sound. 17. Think Critically Two musical notes have the same pitch and volume. However, they sound very different from each other. How is this possible? 18. Calculate Frequencies A string on a guitar vibrates with a frequency of 440 Hz. Two beats per second are heard when this string and a string on another guitar are played at the same time. What are the possible frequencies of vibration of the second string?

15) pulsing happens when two instruments are close to the same pitch and is called beats. 16) The flute vibrates air in a column. A violin vibrates a string. A kettle drum vibrates a membrane. 17) The two notes have different sound qualities. 18) 438 Hz or 442 Hz

18. MAIN Idea Describe the path that light waves take when you see your image in a mirror. 19. Compare the loudness of sound waves that constructively interfere with the loudness of sound waves that destructively interfere. 20. Describe how one tuning fork's vibrations can cause another tuning fork to vibrate. 21. Infer Sound waves often bend around columns in large concert halls. Is this a result of refraction or diffraction? 22. Think Critically Suppose the speed of light was greater in water than in air. Draw a diagram to show whether an object under water would seem deeper or closer to the surface than it actually is. 23. Calculate Angle of Incidence The angle between a flashlight beam that strikes a mirror and the reflected beam is 80 degrees. What is the angle of incidence?

18) Light waves travel from a light source where some of them reflect off you. Some of those light waves that travel to the mirror where they reflect off the mirror. Some of these light waves then travel from the mirror to your eye. 19) Sound waves will be louder where they constructively interfere and softer whey they destructively interfere. 20) This can occur if both tuning forks are tuned to the same frequency, so they both have the same natural frequency. The vibrations of one tuning fork will cause the air around the other tuning fork to vibrate at the natural frequency of both tuning forks. The second tuning fork will absorb this energy and start to vibrate. This is called resonance. 21) Diffraction 23) 80 degrees

19. MAIN Idea Describe at least three different ways that people use sound. 20. Describe some differences between a gym and a concert hall that might affect the amount of reverberation in each. 21. Compare and contrast echolocation and sonar. 22. Explain how ultrasonic imaging works. 23. Think Critically How might sonar technology be useful in locating deposits of oil and minerals? . 24. Calculate Distance Sound travels at about 1,500 m/s in seawater.How far will a sonar pulse travel in 46 s? 25. Calculate Time How long will it take for an undersea sonar pulse to travel 3 km?

19) to locate objects under water, to diagnose problems, to treat medical ailments 20) Concert halls usually have soft features and are designed for musical enjoyment. Gyms are usually hard and have sharp angles. 21) Both are used to locate objects. Ecolocation is based on living things. Sonar relies in mechanical equipment. 22) Ultrasound is directed toward an object. The sound ways reflect off the target and are used to produce an electronic signal. A computer converts the signals into images call sonograms 23) Sound waves could be reflected from the oil. They would also travel at different speeds through different materials 24) 69 km 25) . 2s

23. MAIN Idea Discuss how optical fibers are used to transmit telephone conversations. 24. Contrast polarized and unpolarized light. 25. Describe how a hologram is made. 26. Identify all the conditions that are necessary for total internal reflection to occur. 27. Think Critically On a sunny day, you are looking at the surface of a lake through polarized sunglasses. How could you use your sunglasses to tell if the light reflected from the lake is polarized? 28. Calculate Number of Fibers An optical fiber has a diameter of 0.3 mm. How many fibers would be needed to form a cable with a square cross section, if the cross section was 1.5 cm on a side?

23). Sounds are converted into an electric signal. The signal is then converted into pulses of light. Those pulses travel through fiber optic cable, and converted back into electrical signals, and then converted back into sound 24) For polarized light, the magnetic fields can vibrate in one direction. For unpolarized light, the magnetic fields can vibrate in any direction. 25) An object is illuminated with a laser. The reflected light interferes with another beam of laser light. This interference is recorded on photographic film. When a laser shines on the film, a hologram is produced. 26) It must occur at a boundary between two materials. Light must travel slower in the present material than in the other material. The angle of incidence must be greater than the critical angle. 27) Tilt you head sideways; rotate the lenses by 90°. If the lake appears noticeably darker or brighter, then the light reflected from the lake is polarized. 28) 2,500

8. MAIN Idea Explain why a white fence appears to be white. In your answer, include the colors of light that your eye detects and tell how your brain interprets those colors. 9. Identify what color would be seen if equal amounts of red light and green light were mixed. 10. Compare and contrast the primary colors of light and the primary pigment colors. 11. Describe how your eyes detect color. 12. Think Critically Light reflected from an object passes through a green filter, then a red filter, and finally a blue filter. What color will the object appear to be? 13. Use Percentages In the human eye, there are about 120,000,000 rods. If 90,000,000 rods trigger at once, what percent of the total number of rods are triggered? 14. Convert Units The wavelengths of a color are measured in nanometers (nm), which is 0.000000001 meters (one-billionth of a meter). Find the wavelength in meters of a light wave that has a wavelength of 690 nm.

8) White fences reflect all colors. Your eye sees three colors and all three get activated. The brain interprets this as white light 9) yellow 10) Primary colors are red, green, & blue. Primary pigments are magenta, yellow, & cyan. Equally mix primary colors and you get white. Equally mix the primary pigments and you get black. 11) Cones in your retina detect light of specific wave lengths, which your brain detects as colors. Red cones detect red & yellow light, green cones detect yellow and green light, blue cones detect blue & violet light. 12) black 13) 75% 14) 0.000,000,69 nm

8) Determine which will change if you turn up a radio's volume: wave velocity, intensity, pitch, frequency, wavelength, loudness. Explain. 9. Identify the range of human hearing in decibels and the level at which sound can damage human ears. 10. Compare and contrast frequency and pitch. 11. Draw and label a diagram that explains the Doppler effect. 12. Think Critically Why would a passing car exhibit a greater sound frequency change when it moves at 30 m/s than when it moves at 12 m/s?

8) intensity, loudness The higher the intensity and amplitude, the louder the sound, so when you turn up the volume, Intensity and amplitude increases. 9) Noise levels are measured in Decibles. The higher the decibel level, the louder the noise. Sound that are louder than 85 dB can cause permanent hearing loss. 10) Frequency is the number of times a vibration occurs each second. Pitch is the human perception of how high or low a sound is and depends primarily on frequency. The higher the frequency the higher the pitch. 11) 12) The velocity change would be greater so the frequency change would be greater

Concave Lenses

A concave lens is a lens that is thinner in the middle and thicker at the edges. As shown in Figure 11, light rays that pass through a concave lens bend outward, away from the optical axis. The rays spread out and never meet at a focal point, so they never form a real image. However, a concave lens can form virtual images. These virtual images are always upright and smaller than the actual object. Notice that concave lenses and convex mirrors both produce the same types of images. Concave lenses are used in some types of eyeglasses and in some microscopes. Concave lenses are usually placed in combination with other lenses. A summary of the images formed by concave and convex lenses is shown in Table 2.

Mirrors that magnify

A concave mirror magnifies an object when you place that object between the concave mirror and that mirror's focal point. Figure 7 shows that the reflected rays diverge and a virtual image forms. Just as it does with a plane mirror, your brain interprets the diverging rays as if they came from one point behind the mirror. You can find this point by imagining virtual rays that extend behind the mirror. The resulting image is magnified. Shaving mirrors and makeup mirrors are concave mirrors that are used for magnification. They form enlarged, upright images of a person's face so that it is easier to see small details.

Amplitude

A measure of energy in a wave. The more energy a wave carries= greater amplitude Distance from crest or trough to normal postion in transverse waves. The deeper the compression, the larger the amlitude of the compression The measure of the size of the disturbance from a wave. If the wave's amplitude is greater, then the disturbance from the wave is also greater. Measured differently for longitudinal and transverse waves. Longitudinal Waves: Is related to how tightly the medium is pushed together at the compressions and how much the medium is pulled apart at the rarefactions. The more tightly the medium is at the compressions, the larger the wave's amplitude is. Another indicator of high amplitude is whether the medium is stretched out more in the rarefactions. Transverse Waves: The vertical distance from crest or trough of a wave to the rest positon of the medium. The amplitude of any transverse wave is also half the vertical distance from crest to trough.

Musical Instruments

A musical instrument is any device used to produce a musical sound. Violins, cellos, oboes, bassoons, horns, flutes, and kettledrums are musical instruments that you might have seen and heard in your school orchestra. The members of a jazz band might play clarinets, trumpets, and saxophones. You have probably also heard guitars, pianos and keyboards, and banjos. These familiar examples form just a small sample of the diverse assortment of instruments that people play throughout the world. For example, Australian Aborigines accompany their songs with a woodwind instrument called the didgeridoo (DIH juh ree dew). Caribbean musicians use rubber-tipped mallets to play steel drums, and a flutelike instrument called the nay is played throughout the Arab world. Strings Compared to the overall history of musical instruments, string instruments are quite modern. The first manufactured string instruments probably did not appear until about 6,000 years ago. Today, you might hear soft violins, screaming electric guitars, and elegant harps. In string instruments, sound is produced by plucking, striking, or drawing a bow across tightly stretched strings. Because the sound of a vibrating string is soft, almost all string instruments include a way to amplify sound. Many string instruments, such as the violin in Figure 14, have a resonator. A resonator (RE zuh nay tur) is a hollow chamber filled with air that amplifies sound when the air inside of it vibrates. Other string instruments, such as electric guitars, have pick-ups. Pick-ups convert the sound from strings into electric signals. These signals are then amplified before being converted back into sound. Wind and brass instruments The vibrations of air inside of wind and brass instruments determine the frequencies that those instruments produce. These instruments have been around for much longer than string instruments. Humans created their first wind instruments at least 30,000 years ago. Some scientists think that the first wind instruments may have been created more than 45,000 years ago. The largest wind instrument today is the pipe organ. The Wanamaker Organ, a small part of which is shown in Figure 15, has more than 28,000 pipes. Other modern brass and wind instruments include tubas, horns, oboes, and flutes. All brass and wind instruments use various methods to make air vibrate inside the instrument. For example, a flute player blows a stream of air over the edge of the flute's mouth hole. This causes the air inside the flute to vibrate. For an instrument such as a saxophone, the player blows across a reed, causing it to vibrate. The vibrating reed then causes the air in the instrument to vibrate. For a brass instrument, such as a trumpet, the musician vibrates his or her lips to make the air inside the instrument vibrate. In brass and wind instruments, the length of the vibrating tube of air determines the pitch of the sound produced. In flutes and trumpets, the musician changes the length of the resonator by opening and closing finger holes or valves. In a trombone, the tubing slides in and out to become shorter or longer. Percussion Does the sound of a bass drum make your heart start to pound? Percussion instruments are probably the oldest of all instruments other than the human voice. Since ancient times, people have used drums and other percussion instruments to send signals, accompany important rituals, and entertain one another. Percussion instruments are struck, shaken, rubbed, or brushed to produce sound. Some, such as the marching band drums shown in Figure 16, have a membrane stretched over a resonator. When the drummer strikes the membrane, the membrane vibrates and causes the air inside the resonator to vibrate. The resonator amplifies the sound made when the membrane is struck. Some drums have a fixed pitch, but others have a pitch that can be changed by tightening or loosening the membrane. Caribbean steel drums and xylophones are both examples of percussion instruments where you can control the pitch of the instrument. Caribbean steel drums were developed in the 1940s in Trinidad. As many as 32 different striking surfaces hammered from the ends of 55-gallon oil barrels create different pitches of sound. The side of a drum acts as the resonator. The xylophone shown in Figure 17 is another type of percussion instrument. It has a series of wooden bars, each with its own tube-shaped resonator. The musician strikes the bars with mallets that affect the sound quality. Hard mallets make crisp sounds, while softer rubber mallets produce sounds that are more like the drops of water from a leaky faucet. Other types of percussion instruments include cymbals, rattles, and even oldfashioned washboards.

Nearsightedness

A person who is nearsighted can see objects clearly only when those objects are nearby. Objects that are far away appear blurred. In a nearsighted eye, the cornea and the lens form a sharp image of a distant object before the light reaches the retina, as shown in Figure 15. To correct this problem, a nearsighted person can wear concave lenses. Figure 15 shows how a concave lens causes incoming light rays to diverge before they enter the eye. Then the light rays from distant objects can be focused by the eye to form a sharp image on the retina and not in front of it.

Wave

A repeating disturbance that transfers energy through matter or space

Prisms

A sparkling glass prism hangs in a sunny window, refracting the sunlight and projecting a colorful pattern onto the walls of the room. How does the bending of light create these colors? It occurs because the amount of bending usually depends on the wavelength of the light. Wavelengths of visible light range from the longer red waves to the shorter violet waves. White light, such as sunlight, is composed of this whole range of wavelengths. Figure 5 shows what occurs when white light passes through a prism. The triangular prism refracts the light twice—once when it enters the prism and again when it leaves the prism and reenters the air. Because a longer wavelength of light has a smaller index of refraction, it is refracted less than a shorter wavelength. As a result of these different amounts of bending, the different colors are separated when they emerge from the prism. Red light is bent the least

Microscopes

A telescope would be useless if you were trying to study the cells in a butterfly wing, a sample of pond scum, or the differences between a human hair and a horse hair. You would need a microscope to look at such small objects. A microscope is a device that uses two convex lenses with relatively short focal lengths to magnify small, close objects. A microscope, like a telescope, has an objective lens and an eyepiece lens. However, it is designed differently because the objects viewed are close to the objective lens. Figure 20 shows a simple microscope. The object to be viewed is placed on a transparent slide and is illuminated from below. The light passes by or through the object on the slide and then travels through the objective lens. The objective lens is a convex lens. It forms a real, enlarged image of the object because the distance from the object to the lens is between one and two focal lengths. The real image is then magnified again by the eyepiece lens (another convex lens) to create a virtual, enlarged image. This final image can be hundreds of times larger than the actual object, depending on the focal lengths of the two lenses. The total magnification is the magnification of the objective times the magnification of the eyepiece

Matter and Electromagnetic Waves

All matter contains charged particles that are always in motion. As a result, all objects emit electromagnetic waves. Objects can emit electromagnetic waves at many wavelengths. However, the dominant wavelength emitted becomes shorter as the temperature of the material increases.

Intensity

Amount of energy that flows through a certain a rea in a given amount of time.

Carrier waves transmit a signal in one of two ways which are?

Amplitude Modulation (AM): AM radio broadcasts information by varying the amplitude of th carrier wave. Frequency Modulation (FM): FM Radio waves caries the frequency of carrier.

Vibrations and Sound

An amusement park can be a noisy place. The sounds from the rides and games can make it hard to hear what your friends say. All of these sounds have something in common: a vibrating object produces each one. For example, your friends' vibrating vocal cords produce their voices. Vibrating speakers produce the music from a carousel.

Radar

Another use for radio waves is to find the position and movement of objects by a method called radar. Radar stands for RAdio Detecting And Ranging. With radar, radio waves are transmitted toward an object. By measuring the time required for the waves to bounce off the object and return to a receiving antenna, the location of the object can be found. Radar is used for tracking the movement of aircraft, watercraft, and spacecraft, as shown in Figure 8. Law enforcement officers also use radar to measure how fast a vehicle is moving.

Light and the eye

As shown in Figure 9, light enters a healthy eye through the lens and is focused on the retina, an area on the inside of your eyeball. The retina is composed of two types of cells that absorb light. When these cells absorb light, chemical reactions convert light's radiant energy into nerve impulses that are transmitted to the brain. One type of cell in the retina, called a cone, allows you to distinguish colors and detailed shapes of objects. Cones are most effective in daytime vision. The second type of cell, called a rod, is sensitive to dim light and is useful for night vision. Your eyes have three types of cones, each of which responds to a different range of wavelengths. Red cones respond mostly to red and yellow, green cones respond mostly to yellow and green, and blue cones respond mostly to blue and violet.

Echolocation

At night, bats swoop around in darkness without bumping into anything. They even manage to find insects and other prey in the dark. Most species of bats depend on echolocation. Echolocation is the process of locating objects by emitting sounds and then interpreting the sound waves that are reflected from those objects. Figure 20 explains more about echolocation.

Television

Audio is sent by a FM Radio waves and video is sent by AM radio signals Cathode ray tubes- Produce images you see on Tv. Surface is covered by spots that glow red, green, or blue when struck by electron beams.

Particles as waves

Because electromagnetic waves could behave as particles, other scientists wondered whether particles, such as electrons, could behave as waves. If a beam of electrons was sprayed at two tiny slits, you might expect that the electrons would strike only the area behind the slits, like the spray paint at the left of Figure 6. But scientists found that the electrons formed an interference pattern typical of waves, as seen in the right of Figure 6. When waves pass through narrow slits, they interfere with each other. This experiment showed that electrons can behave like waves. It is now known that all particles can behave like waves. However, this does not mean that particles travel in wavy lines. Rather, this means that they display behavior, such as interference, that was once associated only with waves

Give two real world examples of refraction of light

Camera and Microscope

What kind of waves are sound waves

Compressionaly waves formed from vibrating objectsc ollding with air molecules.

Lens table

Convex ---> object beyond two focal lengths -----> Real ---> Inverted -----> smaller Object between 1 and two focal lengths ----> Real ----> Inverted -----> larger Object within one focal length -----> virtual -----> upright ----> larger Concave ----> object at any positions ----> virutal ----> upright ----> smaller

The parts of a wave (Transverse)

Crest: The high points of a transverse wave. Troughs: Low points of a transverse wave. The imaginary line that is half the vertical distance between a crest and a trough is the rest position.

Elasticity and sound speed

Elasticity is the tendency of an object to rebound to its original state when it is deformed. A rubber ball is elastic. It tends to spring back to its original shape after someone squeezes it. A ball of clay is much less elastic. Elastic objects also rebound more quickly when sound waves travel through them. Therefore, sound waves travel more quickly through elastic objects. Usually, solids are more elastic than liquids and liquids are more elastic than gases. This is another reason why sound waves typically travel fastest through solids, slower through liquids, and slowest through gases. Read

Telephones

Electrical signal creates radio wave that is transmitted to and from a microwave

Electromagnetic Waves

Electromagnetic waves are made by vibrating electric charges. Electromagnetic waves are composed of changing electric fields and magnetic fields. Instead of transferring energy from particle to particle, electromagnetic waves travel by transferring energy between the electric and magnetic fields. Electromagnetic waves do not require matter to travel because electric fields and magnetic fields can exist where matter is not present.

A Range of Frequencies

Electromagnetic waves have a wide variety of frequencies. They might vibrate once each second or trillions of times each second. The entire range of electromagnetic wave frequencies is called the electromagnetic spectrum. A spectrum is a continuous sequence arranged by a particular property. Each region of the electromagnetic spectrum has a specific name, as shown in Figure 7. Each region interacts with matter differently. The human eye detects only a small portion of the electromagnetic spectrum called visible light. Various devices have been developed to detect other frequencies. For example, the antenna of your radio detects radio waves

Microwaves

Electromagnetic waves with wavelengths between 0.1 mm and 30 cm are called microwaves. Microwaves with wavelengths of about 1 cm to 20 cm are widely used for communication, such as for cellular telephones and satellite signals. However, you are probably most familiar with microwaves because of their use in microwave ovens. Microwave ovens In a microwave oven, microwaves interact with the water molecules in food, as shown in Figure 10. Each water molecule has a slight positive charge on one side and a slight negative charge on the other side, so it will align in an electric field. The vibrating electric field inside a microwave oven causes water molecules in food to rotate back and forth billions of times each second . This rotation causes a type of friction between water molecules that generates thermal energy. The thermal energy produced by the water molecules interactions causes your food to cook. Foods with plenty of water cook well in the microwave. Frozen water, however, cannot be warmed using microwaves because the water molecules are bound in a crystallized structure and cannot rotate. On many microwave ovens, there is a special defrost setting. This setting heats the partly melted water on the surface of the food. The inside of the food is then warmed by conduction until all the water is liquid again.

X-rays

Electromagnetic waves with wavelengths between about ten billionths of a meter and ten-trillionths of a meter are called X-rays. X-rays have shorter wavelengths than UV waves and their photons have larger energies. X-rays penetrate skin and soft tissue but not denser materials, such as teeth and bones. Doctors and dentists use low doses of X-rays to form images, like the one in Figure 16, of bones and teeth. X-rays are also used in airport screening devices to examine the contents of luggage.

Gamma Rays

Electromagnetic waves with wavelengths shorter than about 100-trillionths of a meter are called gamma rays. Gamma rays have high frequencies and have the highest-energy photons. They have enough energy to penetrate several centimeters of lead. Gamma rays are produced by processes that occur in the nuclei of atoms. Both X-rays and gamma rays are used in a technique called radiation therapy to kill diseased cells in the human body. A beam of X-rays or gamma rays can damage the biological molecules in living cells, causing both healthy and diseased cells to die. By carefully controlling the amount of X-ray or gamma ray radiation and focusing it on the diseased area, the damage to healthy cells can be reduced during treatment. Figure 17 shows a patient receiving radiation to treat cancer. The gamma rays are focused on the tumor and kill the cancer cells, while doing little damage to the surrounding healthy cells.

Radio Waves

Even though you cannot see them, radio waves are all around you. Radio waves are electromagnetic waves with wavelengths longer than 10 cm. Radio waves have long wavelengths and low frequencies, and their photons have low energies. Radio waves have many uses, including communications and medical imaging

Light is necessary for

Eyes to see. Light waves spread in all direction from a light

Efficient lighting

Fluorescent lights use as little as one-fifth of the electrical energy to produce the same amount of light as incandescent bulbs. Fluorescent bulbs also last much longer than incandescent bulbs. This higher efficiency can mean lower energy costs over the life of the bulb. Reduced energy usage could reduce the amount of fossil fuels that are burned to generate electricity. This would also decrease the amount of carbon dioxide and pollutants released into Earth's atmosphere. Hospitals, schools, office buildings, and factories have been using long, tube-shaped fluorescent bulbs for many years. Many homes are now using compact fluorescent bulbs, which can be screwed into traditional lightbulb sockets. This gives consumers one way to save energy without having to replace the entire light fixture.

Seismic waves

Forces within Earth's interior can cause regions of Earth's crust to move, bend, or even break. Movement in the crust, which occurs along faults, can result in a rapid release of energy. This energy travels away from the fault in the form of seismic (SIZE mihk) waves, as shown in Figure 6. Seismic waves can be longitudinal waves or transverse waves. Scientists have found out much about Earth's interior by studying these seismic waves. Seismic waves can travel through Earth, as well as along Earth's surface. When the energy from seismic waves is transferred to objects on Earth's surface, those objects move and shake.

Pitch is the human perception of a waves

Frequency

Calculating Wave speed (m/s)

Frequency (Hz) x Wavelength f= fy

Frequency and pitch

Frequency is a measure of how many wavelengths pass a particular point each second. For a longitudinal wave, such as sound, the frequency is the number of compressions or the number of rarefactions that pass by each second. Frequency is measured in hertz (Hz). One Hz means that one wavelength passes by in one second. When sound waves with high frequency reach your ears, many compressions reach your eardrums each second. The waves cause your eardrums and all the other parts of your ears to vibrate more quickly than a sound wave with a low frequency. Your brain interprets these fast vibrations caused by high-frequency waves as a sound with a high pitch. As the frequency of sound waves decreases, the pitch becomes lower. Figure 9 shows different notes and their frequencies. Notice that when you sing do, re, mi, fa, so, la, ti, do, the second do has twice the frequency of the first do. Animals differ in their sensitivities to different ranges of sound frequencies. A human teenager with typical hearing can hear sounds with frequencies from about 20 Hz to 20,000 Hz. However, the highest frequency that a typical human can hear decreases with age. The human ear is most sensitive to sounds in the range of 440 Hz to about 7,000 Hz. This roughly corresponds to the notes on the upper half of a piano. Dogs can hear sounds with frequencies up to about 35,000 Hz, and bats can detect frequencies higher than 100,000 Hz

The Global Positioning System

Getting lost while hiking is not uncommon; but if you are carrying a Global Positioning System receiver, it is much less likely to happen. The Global Positioning System (GPS) is a system of satellites, ground monitoring stations, and receivers that determine your exact location at or above Earth's surface. The 24 satellites necessary for 24-hour, around-the-world coverage became fully operational in 1995. Figure 26 illustrates how these satellites are arranged in orbit. Signals from four satellites are used to determine the location of an object using a GPS receiver. GPS satellites are owned and operated by the United States Department of Defense, but the microwave signals they send out can be used by anyone. Several other countries are working to develop similar systems. Airplanes, ships, cars, and cell phones can use GPS for navigation. Some pet collars also contain GPS receivers. If the pet runs away or is lost, the GPS receiver in the collar can be used to locate the animal.

Plane Mirrors

Greek mythology tells the story of a handsome young man named Narcissus who noticed his image in a pond and fell in love with himself. Like pools of water, mirrors are smooth surfaces that reflect light to form images. Just as Narcissus did, you can see yourself as you glance into a quiet pool of water or walk past a shop window. Most of the time, however, you probably look for your image in a flat, smooth mirror. A flat, smooth mirror is a plane mirror. Reading Check Define What is a plane mirror? Reflections from plane mirrors What do you see when you look into a plane mirror? Your reflection is upright. If you were one meter in front of the mirror, your image would appear to be one meter behind the mirror, or two meters from you. You might notice that the reflection of any writing in a plane mirror appears backward. Figure 2 shows how you see yourself in a plane mirror. First, light rays from a light source strike you. Every point that is struck by the light rays reflects these rays so they travel outward in all directions. If your friend were looking at you, these reflected light rays coming from you would enter her eyes so she could see you. However, if a mirror is placed between you and your friend, the light rays are reflected from the mirror into your eyes.

Beats

Have you ever heard two flutes play the same note when they were not properly tuned? You might have heard a pulsing variation in loudness. This variation in loudness is called beats and can be unpleasant to the listener. As shown in Figure 18, when compressions and rarefactions overlap each other, loudness decreases. When compressions overlap compressions, loudness increases. If two waves of different frequencies interfere, a new wave is produced that has a different frequency. The frequency of this wave is the difference between the frequencies of the two component waves. The frequency of the beats that you hear decreases as the two waves become closer in frequency. If two flutes play a note at the same frequency, no beats are heard.

Light and Vision

Have you ever tried to find an address on a house or an apartment at night on a poorly lit street? It is harder to do those activities in the dark than it is when there is plenty of light. Your eyes see by detecting light, so when you can see something, it is because light came from that object to your eyes. Light is emitted from a light source, such as the Sun or a lightbulb, and then reflects off an object, such as the page of a book, as shown in Figure 1. When light travels from an object to your eye, you see the object. Light can reflect more than once. For example, light can reflect off an object into a mirror and then reflect into your eyes. When no light is available to reflect off objects and into your eyes, you cannot see anything. This is why it is hard to see an address in the dark. Light rays Light sources send out light waves that travel in all directions. These waves spread out from the light source, just as ripples on the surface of water spread out from the point of impact of a pebble. You could also think of the light coming from the source as traveling in narrow beams. Each narrow beam travels in a straight line and is called a light ray. Even though light rays can change direction when they are reflected or refracted, your brain interprets images as if light rays travel in a straight line.

Focusing on near and far

How can your eyes focus both on close objects, such as the watch on your wrist, and distant objects, such as a clock across the room? For you to see an object clearly, its image must be focused sharply on your retina. However, the retina is always a fixed distance from the lens. Remember that the location of an image formed by a convex lens depends on the focal length of the lens and the location of the object. For an image to be formed on the retina, the focal length of the lens needs to be able to change as the distance to the object changes. The lens in your eye is flexible, and muscles attached to it change its shape and its focal length. This is why you can see objects that are near and far away. Look at Figure 13. When you focus on an object far from your eye, the muscles around the lens relax. This pulls the lens into a less convex shape. When you focus on a nearby object, these muscles make the lens more curved, causing the focal length to decrease.

Pitch

How high or low a sound seems to be which is related to frequency of a sound wave. Subsonic: < 20 hz Human can hear: 20-20,000 Hz Ultrasonic > 20,000

Diffraction and wavelength

How much does a wave bend when it strikes an object or an opening? The amount of diffraction that occurs depends on how big the obstacle or opening is compared to the wavelength, as shown in Figure 20. When an obstacle is roughly the same size as or smaller than the wavelength of a wave, the wave bends around it. But when the obstacle is much larger than the wavelength, the waves do not diffract as much. If the obstacle is much larger than the wavelength, almost no diffraction occurs. Instead, the obstacle casts a shadow. Hearing around corners Suppose you are walking down the hallway, and you hear sounds coming from a classroom on the left before you reach the open classroom door. However, you cannot see into the room until you reach the doorway. Why can you hear the sound waves but not see the light waves while you are still in the hallway? The wavelengths of sound waves are similar in size to a door opening. Sound waves diffract around the door and spread out down the hallway. Light waves have a much shorter wavelength. They are hardly diffracted at all by the door. So, you cannot see into the room until you get to the door. Diffraction of radio waves Diffraction also affects your radio's reception. AM radio waves have longer wavelengths than FM radio waves do. Because of their longer wavelengths, AM radio waves diffract around obstacles, such as buildings and mountains. The FM waves with their short wavelengths do not diffract as much. As a result, AM radio reception is often better than FM reception around tall buildings and natural barriers, such as hills

Refraction

If a wave is traveling at an angle when it passes from one medium to another, it changes direction or bends, as it changes speed. It is the bending of a wave caused by a change in its speed as it travels from one medium to another. The greater the change speed, the more the wave bends. When light travels from air to water, they slow down and bend toward the normal. When light waves travel fom water to air, they sped up and bend away from the normal.

Color blindness

If one or more of your sets of cones did not function properly, you would not be able to distinguish between certain colors. About eight percent of men and one-half percent of women have a form of color blindness. Most people who are said to be color-blind are not truly blind to color, but they have difficulty distinguishing between a few colors, most commonly red and green. Figure 10 shows an example of a red-green color blindness test. Because these two colors are used in traffic signals, severely color-blind drivers and pedestrians must use the position of the light, instead of color, to know when to stop and go.

Sound in liquids and solids

If you have been underwater and heard garbled voices, you know that sound travels through water as well as air. If you have put your ear to your desk and heard sounds, you know that sound travels through solids. Sound waves travel through any type of matter—solid, liquid, or gas. The matter through which a wave travels is called the medium. A sound wave produces compressions and rarefactions in a medium as it travels through that medium. What happens when there is no matter through which sound can travel? Could sound be transmitted without matter to compress, expand, and collide? In order for astronauts, such as the ones in Figure 2, to talk to each other, they must use electronic communication equipment because there is no atmosphere to transmit sound waves. Sound waves cannot travel through the vacuum of outer space.

Mixing Colors

If you have ever browsed through a paint store, you have probably seen displays where customers can select paint samples of almost every imaginable color. For example, you might have mixed blue and yellow paint to produce green paint. What would happen if you mixed blue and yellow light? Would you get green light? Mixing colored lights From the glowing orange of a sunset to the deep blue of a mountain lake, all the colors that you see can be made by mixing three colors of light. These three colors—red, green, and blue—are the primary colors of light. They correspond to the three different types of cones in the retina of your eye. When they are mixed together in equal amounts, they produce white light, as Figure 12 shows. Mixing the primary colors in different proportions produces all the colors that you see. Reading Check Identify the primary colors of light. Paint pigments If you mixed equal amounts of red, green, and blue paint, would you get white paint? If mixing colors of paint were like mixing colors of light, you would. But mixing paint is different. The variety of colors of paint is a result of mixtures of pigments. A pigment is a colored material that is used to change the color of other substances. The color of a pigment results from the different wavelengths of light that the pigment reflects. Paint pigments are usually made of chemical compounds. For example, titanium oxide is a bright white pigment that reflects all colors of light. Another example is lead chromate, which is used to make paint for yellow lines on highways. Other colors can be obtained by mixing various pigments together.

Pitch

If you have ever studied music, you are probably familiar with the musical scale do, re, mi, fa, so, la, ti, do. If you were to sing this scale, your voice would start low and become higher with each note. As you sang, you would have heard a change in pitch. Pitch is how high or low a sound seems to be. The notes on the right side of a piano have high pitches. The pitch of a sound is primarily related to the frequency of the sound waves.

Wavelength is related to frequency

If you make transverse waves with a rope, you increase the frequency by moving the rope up and down faster. Moving the rope faster also makes the wavelength shorter. This relationship is always true. As frequency increases, wavelength decreases. If you double the frequency of a wave you halve the wavelength. If you double the wvaelength you halve the frequency. The frequency of a wave is always equal to the rate of vibration of the source that creates it. If you move the rope up, down and back up in 1s, the frequency you have is 1Hz. If you move the rope up, down, and back up five times in 1s, the resulting wave has a frequency of 5Hz.

Space telescopes

Imagine being at the bottom of a swimming pool and trying to read a sign by the pool's edge. The motion of the water in the pool would distort your view of any object beyond the water's surface. In a similar way, Earth's atmosphere distorts the view of objects in space. To overcome the blurriness of humans' view into space, the National Aeronautics and Space Administration (NASA) built a telescope called the Hubble Space Telescope and launched it into space, high above Earth's atmosphere. Because Hubble is above Earth's atmosphere, it has produced incredibly sharp and detailed images. Figure 19 shows the difference in the images produced by telescopes on Earth and the Hubble telescope. With the Hubble Space Telescope, scientists can detect light from planets, stars, and galaxies that would otherwise be scattered by Earth's atmosphere. Hubble is not the only space telescope. Other space telescopes, such as the Chandra X-Ray Observatory and the Spitzer Space Telescope, help scientists study the universe through X-ray and infrared radiation. Reading Check Explain why a space telescope is able to produce clearer images than telescopes on Earth. The Hubble telescope is a type of reflecting telescope that uses two mirrors to collect and focus light to form an image. The primary mirror in the telescope is 2.4 m across. A next generation space telescope, called the James Webb Space Telescope, is due to be launched in 2014. The primary mirror on the James Webb Space Telescope will be 6.5 m across

The Doppler Effect

Imagine that you are standing at the side of a racetrack with race cars zooming past. When the cars are moving toward you, the pitches of their engines are higher. When the cars are moving away from you, the pitches are lower. The Doppler effect is the change in wave frequency due to a wave source moving relative to an observer or an observer moving relative to a wave source. Figure 10 shows how the Doppler effect occurs Moving sound sources As a race car moves, it sends out sound waves in the form of compressions and rarefactions. In the top panel of Figure 10, the race car produces a compression labeled A as that race car speeds toward the flagger. Compression A travels through the air toward the flagger. By the time compression B leaves the race car in the bottom panel of Figure 10, the car has moved forward. Because the car has moved since the time it created compression A, compressions A and B are closer together in front of the car. Because the compressions are closer together, the frequency is higher and the flagger hears a higher pitch. The compressions behind the moving car are farther apart, resulting in the flagger observing a lower pitch after the car passes. Moving observers You can also observe the Doppler effect when you are moving past a sound source that is standing still. Suppose you were riding in a school bus and you passed a building with a ringing bell. The pitch would sound higher as you approached the building and lower as you rode away from it. The Doppler effect happens any time a sound source is moving relative to an observer. It occurs whether the sound source or the observer is moving. The faster the change in position, the greater the change in frequency and pitch. Electromagnetic waves and the Doppler effect The Doppler effect also occurs for other waves besides sound waves. For example, the frequency of electromagnetic waves changes if an observer and wave source are moving relative to each other. Astronomers use the Doppler effect to help measure the motions of stars and other objects. In addition, police radar guns, such as the one shown in Figure 11, use the Doppler effect to measure the speeds of cars. The radar gun sends radar waves toward a moving car. The waves are reflected from the car and their frequency is shifted, depending on the speed and direction of the car. From the Doppler shift of the reflected waves, the radar gun determines the car's speed

Amplifying light

In a helium-neon laser, a mixture of helium and neon gases is sealed in a tube with mirrors at both ends. These atoms absorb radiant energy from a flashtube, which is a device that produces a short, bright flash of light. The atoms then release their excess energy by emitting light waves of a certain wavelength. The light waves are emitted in all directions. Most of the waves escape through the sides of the tube, but those traveling along the tube are reflected between the two mirrors. As they travel, these light waves stimulate other atoms to emit more light waves. The result is an increase in the amount of light traveling back and forth along the tube. To allow a small amount of the light out of the tube, one of the mirrors is coated only partially with reflective material. A narrow, intense laser beam is emitted from the partially reflective end of the tube. Figure 17 illustrates how a laser creates a beam of light.

Sound travels faster in?

In solids and liquid, molcules are close together than gas molecules. As medium temperature rises, molecules move faster conducting sound waves faster.

Optical Scanners

In supermarkets and many other kinds of stores, a cashier passes your purchases over a glass window in the checkout counter, like the one in Figure 25. Or, the cashier might hold a handheld device up to each item. In an instant, the optical scanner beeps and the price of the item appears on a screen. An optical scanner is a device that reads intensities of reflected light and converts the information to digital signals. A supermarket scanner detects a pattern of thick and thin stripes called a bar code. The resulting electrical signal is sent to a computer that searches its database for the item's price and sends the information to the cash register. You may have used another type of optical scanner to convert pictures or text into forms you can use in computer programs. With a flatbed scanner, for example, you lay a document or picture facedown on a sheet of glass and close the cover. An optical scanner passes underneath the glass and reads the pattern of colors. The scanner converts the pattern to an electronic file that can be stored on a computer. Many new photocopiers use scanners like these. The photocopier scans a document and then prints a copy.

Magnetic resonance imaging (MRI)

In the early 1980s, medical researchers developed a technique called magnetic resonance imaging, which uses radio waves to help diagnose illness. The patient lies inside a large cylinder, like the one shown in Figure 9. The cylinder contains a powerful magnet, a radio wave emitter, and a radio wave detector. Protons in hydrogen atoms in bones and soft tissue behave like magnets and align with the strong magnetic field created by the machine's magnet. Some of the protons absorb energy from the radio waves and flip their alignments. The amount of energy a proton absorbs and then re-emits depends on the type of tissue it is part of. A radio receiver detects this released energy. This information is then used to create a map of the different tissues. A picture of the inside of the patient's body is produced painlessly

As the elasticity of a medium increases, the speed of sound ____

Increases

Index of refraction

Indicates how much a material reduces the speed of light; the more light showed the greater the index of refraction. Prisms separate white light into spectrum Light refracted through air layers indifferent densities can result in mirages

Loudness is the human perception of sound wave

Intensity

The decibel scale

It is hard to say how loud is too loud. Two people are unlikely to agree on what is too loud because people vary in their perceptions of loudness. A sound that seems fine to you may seem earsplitting to your teacher. Even so, the intensity of sound can be described using a measurement scale. A decibel (DE suh bel), abbreviated dB, is a unit of sound intensity. The loudest sounds that you hear are probably more than 10 billion times more intense than the softest sounds that you can hear. In order to handle this wide-range of intensities, the decibel measurement scale is set up in a special way. Every increase in 10 dB on the decibel scale represents a tenfold increase in intensity. This means that a 50-dB sound is 10 times more intense than a 40-dB sound. You might think that this means a 60-dB sound is 20 times more intense than a 40-dB sound. However, a 60-dB sound is 10 × 10, or 100, times more intense than a 40-dB sound. A 100-dB sound is 1 0 7 , or 10 million, times more intense than a 30-dB sound. A sound can also have an intensity of less than 0 dB. However, people generally cannot hear these sounds. Sustained sounds above about 90 dB can cause permanent hearing loss. Even short, sudden sounds with intensity levels above 120 dB may cause pain and permanent hearing loss. During some rock concerts, sounds reach this damaging intensity level. Wearing ear protection, such as earplugs, around loud sounds can help protect against hearing loss. Figure 8 shows some sounds and their intensity levels in decibels.

Telephones

Just a few decades ago, telephones had to be connected with wires. Today, cell phones are seen everywhere. When you speak into a telephone, a microphone converts the sound waves into an electric signal. In a cell phone, this signal is transmitted to and from microwave towers using microwaves or radio waves.The towers, like the ones in Figure 23, are several kilometers apart and each covers an area called a cell. If you move from one cell to another, an automated control station transfers the ignal to the new cell and its tower. Transceivers A cell phone is a transceiver. A transceiver transmits one radio signal and receives another radio signal.Using two signals with different frequencies allows you to talk and listen at the same time without interference. Cordless telephones are also transceivers. However, you must remain close to the base unit when using a cordless phone. Another drawback is that if someone nearby is using a cordless telephone at the same frequency, you could hear that conversation on your phone. For this reason, many cordless phones have a channel button that allows you to switch to another frequency. Pagers Some hospitals ban cell phone use because there are concerns that transceivers might interfere with medical equipment. So, many doctors carry small, portable radio receivers called pagers. To contact the doctor, a caller leaves a callback number or a text message at a central terminal. The message is changed into an electronic signal and transmitted by radio waves along with the identification number of the desired pager. The pager receives all messages transmitted at its assigned frequency, but it only responds to messages with its identification number. Restaurants also use pagers, like the one in Figure 24, to notify customers that their tables are ready

Reflection of Light

Just before you left for school this morning, did you glance in a mirror to check your appearance? For you to see your reflection in the mirror, light had to reflect off you, hit the mirror, and reflect off the mirror into your eye. Reflection occurs when a light wave strikes an object and bounces off. The law of reflection Like all waves, light obeys the law of reflection. According to the law of reflection, the angle at which a light wave strikes a surface is the same as the angle at which it is reflected. This law is illustrated in Figure 2. Light reflected from any surface—a mirror or a sheet of paper—behaves this way. Regular and diffuse reflection If light always obeys the law of reflection, why can you see your reflection in a store window but not in a brick wall? The answer involves the smoothness of the surfaces. A smooth, even surface like a pane of glass produces a sharp image by reflecting parallel light waves in only one direction. Reflection of light waves from a smooth surface is regular reflection. A brick wall has an uneven surface that causes incoming parallel light waves to be reflected in many directions, as shown in Figure 3. The reflection of light from a rough surface is diffuse reflection. Diffuse reflection does not produce an image. Microscopic roughness Even a surface that appears to be smooth can be rough enough to cause diffuse reflection. For example, a metal pot might seem to be smooth, but the surface shows rough spots at high magnification, as shown in Figure 4. To cause a regular reflection, the sizes of the surface irregularities must be less than the wavelengths of the light that the surface reflects.

Wave Speed

Light waves travel faster than sound waves which is why you see the impact of a baseball before you hear the sound. The speed of a wave depends on the medium. Sound waves travel faster in liquid, and slower in solids. Light waves travel more slowly in liquids and solids than they do in gases or in a vacuum. Sound waves travel faster if temperature is increases. Equation: Speed (in m/s)= Frequency (in Hz) x wavelength (in m) v= fy V= wave speed f= frequency

Frequency and wavelength

Like all waves, electromagnetic waves can be described by their wavelengths and frequencies. The wavelength of an electromagnetic wave is the distance from one crest to another, as shown in Figure 3. The frequency is the number of wavelengths that pass a point in one second. The units for frequency are hertz. The frequency of an electromagnetic wave equals the frequency of the vibrating charge that produces the wave. This frequency is the number of vibrations of the charge in one second. Electromagnetic waves follow the wave speed equation, v = f λ. As the frequency (f) increases, the wavelength (λ) becomes smaller.

The two types of mechanical waves

Longitudinal and Transverse Waves

Parts of a Longitudinal Wave

Longitudinal waves have no crests or troughs. When it passes through a medium it creates regions where the medium becomes crowed together and more dense, these are compressions. A compression is the more dense region of a longitudinal wave. The less dense region of a longitudinal wave is called a rarefaction.

Light and Matter

Look around your darkened room at night. After your eyes adjust to the darkness, you can see some familiar objects. Brightly colored objects look gray or black in the dim light. If you turn on the light, however, you might see all the objects in the room, including their colors. What you see depends on the amount of light in the room and the color of the objects. To see an object, it must reflect some light into to your eyes. Opaque, translucent, and transparent Objects can absorb, reflect, and transmit light. Objects that transmit light allow light to pass through them. An object's material determines the amount of light it absorbs, reflects, and transmits. The material in the first candleholder in Figure 1 is opaque (oh PAYK). Opaque materials only absorb and reflect light; no light passes through them. As a result, you cannot see the candle. Some materials, such as the second candleholder in Figure 1, are translucent (trans LEW sunt). Translucent materials transmit light but also scatter it. You cannot see clearly through translucent materials, and objects appear blurry. The third candleholder shown in Figure 1 is transparent. Transparent materials transmit light without scattering it, so you can see objects clearly through them

Table 1 Images Formed by Mirrors

Mirror shape: Plane ----> virtual ---> image is creted upright ----> size is same object Concave: objects more than two focal lengths from mirror----> real ----> upside down-----> smaller than object object between one and two focal lengths ----> real----> upside down-----> larger than object object at focal point ----> none ----> none ---->none ----> none object within focal length -----> virtual----> upright ----> larger than object Convex ---> distance of object from mirror: any distance ----> virtual----> image is created upright --->size is smaller than object

How does elasticity affect sound speed? Explain

More elasticity makes the particles get back in regular positions faster so they can collide more often.

Sonar

More than 140 years ago, a ship named the SS Central America disappeared in a hurricane off the coast of South Carolina. In its hold lay ten tons of newly minted gold coins and bars. When the shipwreck occurred, there was no way to search for the ship in the deep water where it sank. The SS Central America and its treasures laid at the bottom of the ocean until 1988, when crews used sonar to locate the wreck under 2,400 m of water. Over $100 million in gold was eventually recovered. Sonar is a system that uses the reflection of underwater sound waves to detect objects. First, a sound pulse is emitted toward the bottom of the ocean. The sound travels through the water and is reflected when it hits something solid, as shown in Figure 21. A sensitive underwater microphone, called a hydrophone, picks up the reflected signal. Because the speed of sound in water is known, the distance to the object can be calculated by measuring how much time passes between emitting the sound pulse and receiving the reflected signal. Reading Check Describe how sonar detects underwater objects. The idea of using sonar to detect underwater objects was first suggested as a way to avoid icebergs, but many other uses have been developed for it. Navy ships use sonar for detecting, identifying, and locating submarines. Fishing crews also use sonar to find schools of fish, and scientists use it to map the ocean floor. More detail can be revealed by using sound waves of high frequency. As a result, most sonar systems are ultrasonic. Ultrasound is sound with frequency above 20,000 Hz and cannot be heard by humans

Infrared Waves

Most of the warm air in a fireplace moves up the chimney, yet you feel the warmth of the blazing fire when you stand in front of a fireplace. Why do you feel the warmth? The warmth you feel is thermal energy transmitted to you by infrared waves. Infrared waves are electromagnetic waves with wavelengths between about one-thousandth of a meter and about 700-billionths of a meter. Using infrared waves Every object emits infrared waves. Hotter objects emit more infrared waves than cooler objects. Infrared detectors can form images of objects from the infrared waves they emit. These images, like the one in Figure 11, can help determine how energy-efficient a structure is. Other devices that use infrared waves include television remote controls and CD-ROM drives.

Making Music

Natural frequencies Every material or object has a particular set of frequencies at which it vibrates. These frequencies are called natural frequencies. Musical instruments employ the natural frequencies of various objects, such as strings, to control pitch. When you pluck a guitar string, the pitch you hear depends on the string's natural frequencies. Each string on a guitar has a different set of natural frequencies. Resonance The sound produced by musical instruments is amplified by resonance. Recall that resonance occurs when a material or an object is made to vibrate at its natural frequencies by absorbing energy from something that is also vibrating at those frequencies. The vibrations of a person's lips in a brass instrument or the reed in a wind instrument cause the air inside the instrument to absorb energy and vibrate at its natural frequencies. The vibrating air makes the instrument sound louder.

Each instrument has a set of

Natural frequencies at which it will vibrate called overtones which produce an instruments distance sound quality.

Concave Mirrors

Not all mirrors are flat like plane mirrors. A concave mirror is a mirror whose surface curves inward. Concave mirrors, like plane mirrors, reflect light waves to form images. However, a concave mirror's curved surface produces different images from a plane mirror's flat surface. Features of concave mirrors A concave mirror has an optical axis. The optical axis is an imaginary straight line drawn perpendicular to the surface of the mirror at the mirror's center. Concave mirrors are made so that every light ray traveling toward the mirror parallel to the optical axis is reflected through a point on the optical axis called the focal point. The focal point for a concave mirror is the point on the optical axis on which light rays that are initially parallel to the optical axis converge after they reflect off the mirror. The distance from the center of the mirror to the focal point is the focal length. Using the focal point and the optical axis, you can diagram how some of the light rays that travel to a concave mirror are reflected, as shown in Figure 4.

Frequency

Number of wavelengths that make pass a fixed point each second. Also the number of times that a point on a wave moves up and down or back and forth each second. You can find the frequency on a longitudinal wave by counting the number of compressions that pass a point each second. Frequency is expressed in hertz(Hz). A frequency of 1Hz means that one wavelength passes by in 1s. In SI units, 1Hz is the same as 1/s. The period of a wave is the amount of tme it takes one wavelength to pass a point. As the frequency of a wave increases, the period decreases. In SI units, period has units of seconds.

Reflection

Occurs when a wave strikes an object and bounces off of it. All types of waves can be reflected. Reflection in a mirror happens first when light strikes her face and bounces off her face. Then the light reflected off her face strikes the mirror and is reflected into her eyes. Echoes: result of reflecting sound waves. Dolphins use clicking noises to learn about their environment. The law of Reflection: The beam striking the mirror is called the incident beam and the beam that bounces off the mirror is called the reflected beam. The line drawn perpendicular to the surface of the mirror is called the normal. The angle formed by the incident beam and the normal is the angle of incidence, labeled i. The angle formed by the reflected beam and the normal is the angle of reflection, labeled r. Angle of Incidence is always equal to angle of reflection. All reflected waves obey this law.

Refraction of light

Occurs when wave of light passes from one medium to another and light wave is bent or refracted.

Refracting telescopes

One common type of telescope is the refracting telescope. A telescope that uses lenses to gather light from distant objects is called a refracting telescope. A simple refracting telescope, shown in Figure 17, uses two convex lenses to gather and focus light from distant objects. Incoming light from distant objects passes through the first lens, called the objective lens. Light rays from distant objects are nearly parallel to the optical axis of the lens. As a result, the objective lens forms a real image at the focal point of the lens, within the body of the telescope. The second convex lens, called the eyepiece lens, magnifies this real image. When you look through the eyepiece lens, you see an enlarged, inverted, virtual image of the real image formed by the objective lens. In order to form detailed images of distant objects, the objective lens of a refracting telescope must be as large as possible. A telescope lens can be supported only around its edge. A large lens can sag or flex due to its own weight, distorting the image that it forms. Another class of telescopes, called reflecting telescopes, do not have this problem. Reflecting telescopes A telescope that uses mirrors and lenses to collect and focus light from distant objects is a reflecting telescope. Mirrors, unlike lenses, can be supported from behind. This additional support for mirrors prevents mirrors from sagging inside reflecting telescopes. As a result, reflecting telescopes can be much larger than refracting telescopes. Figure 18 shows a reflecting telescope. For this reflecting telescope, light from a distant object enters one end of the telescope and strikes a concave mirror at the opposite end. The light reflects off this mirror and converges. Before it converges at a focal point, the light hits a plane mirror inside the telescope tube. The light is then reflected from the plane mirror toward the telescope's eyepiece. The light rays converge at the focal point, creating a real image of the distant object. Just like a refracting telescope, a convex lens in the eyepiece then magnifies this image.

Using optical fibers

Optical fibers are most often used in communications. Telephone conversations, television programs, and computer data can be coded in light beams. Signals cannot leak from one fiber to another and interfere with other messages, so the signal is transmitted clearly. To send telephone conversations through an optical fiber, sound is converted into digital signals consisting of pulses of light from a light-emitting diode (LED) or from a laser. Some systems use multiple lasers, each with its own wavelength, to fit multiple signals into the same fiber. You could send a million copies of your favorite book in one second on a single fiber. Figure 24 shows the size of typical optical fibers. Optical fibers also have medical uses. Doctors use them to explore the inside of the human body. One bundle of fibers transmits light while another carries the reflected light back to the doctor. Physicians can also treat blocked arteries by sending laser light into the body through an optical fiber.

The Retina

Or inner lining of eye converts light into electical signal that brain interprets

Transverse Wave

Particles in the medium move back and forth at right angles to the direction that the wavetravels.

Vision Problems

People with good vision can see objects clearly that are about 25 cm or farther away from their eyes. However, people with the most common vision problems see objects clearly only at some distances, or they see all objects as being blurry. Astigmatism One vision problem, called astigmatism, occurs when the surface of the cornea is unevenly curved. When people have astigmatism, their corneas are more oval than round in shape. Astigmatism causes blurry vision at all distances. Corrective lenses for astigmatism also have an uneven curvature, canceling out the effect of an uneven cornea. Farsightedness Another vision problem is farsightedness. A farsighted person can see distant objects clearly, but cannot bring nearby objects into focus. Light rays from nearby objects do not converge enough after passing through the cornea and the lens to form a sharp image on the retina, as shown in Figure 14. The problem can be corrected with a convex lens that bends light rays so they are less spread out before they enter the eye, also shown in Figure 14. Farsightedness is often related to age. As many people age, the lenses in their eyes become less flexible. The muscles around the lenses still contract as they try to change the shape of the lens. However, the lenses have become more rigid and cannot be made curved enough to focus on close objects. People who are more than 40 years old might not be able to focus on objects closer than 1 m from their eyes.

Intensity

Picture sound waves traveling through the air from a computer's speakers to your ears. If you also picture a rectangle between you and the computer speakers, as in Figure 7, and could measure how much energy passed through the loop in one second, you would measure intensity. Intensity is the amount of energy that passes through a certain area in a specific amount of time. When you turn down the volume on your computer, you reduce the energy carried by the sound waves, so you also reduce their intensity. Distance and intensity Intensity influences how far away a sound can be heard. If you and a friend whisper a conversation, the sound waves you produce have low intensity and are not heard at a far distance. However, when you shout, you can hear each other from much farther apart. The sound waves made by your shouts have high intensity and can be heard farther away. Sound intensity decreases with distance for two reasons. First, the energy that a sound wave carries spreads out as the sound wave spreads out. Second, some of a sound wave's energy converts to other forms of energy, usually thermal energy, as the sound travels through matter. As the sound wave travels farther, more of its energy converts into other forms. Some materials, such as soft, thick curtains, are very effective at converting sound energy to other forms of energy.

Echolocation:

Process of locating objects by emitting sound and interpreting the reflected sound waves (Bats)

List the order of the Electromagnetic Spectrum (R.I.V.U.X.G)

Radio Waves, Infrared waves, Visible light, Ultraviolet waves, X-rays and Gamma rays

Electromagnetic Spectrum includes:

Radio Waves: Low frequency waves with a wavelength of about 1-10 cm. (Radio Stations, Microwaves, radar) Infrared Wave: Have slightly higher frequency than radio waves. Visible Light: Range of electromagnetic waves you can detect with your eyes. (ROYGBIV)- Different colors have different wave lengths Ultraviolet waves- frequencies slightly higher than visible light (Sunburns, vitamin D production, fluorescent materials absorb it, kills materials) X-rays and Gamma rays- Ultra high frequencies that can travel through matter , damage cells (burn images, radiation therapy, )

Radio transmission

Radio converts electromagnetic waves into sound waves

Sodium-Vapor Lights

Sodium-vapor lights are often used for streetlights and other outdoor lighting. Inside a sodium-vapor lamp is a tube that contains a mixture of neon gas, a small amount of argon gas, and a small amount of sodium metal. When the lamp is turned on, the gas mixture becomes hot. The hot gases cause the sodium metal to turn to vapor. The hot sodium vapor emits a yellow-orange glow. Tungsten-Halogen Lights Tungsten-halogen lights are sometimes used to create intensely bright light. These lights have a tungsten filament inside a quartz bulb or tube. The tube is filled with a gas that contains one of the halogen elements, such as fluorine or chlorine. The presence of this gas enables the filament to become much hotter than the filament in an ordinary incandescent bulb. As a result, the light is much brighter. Another advantage of tungsten-halogen bulbs is that they last longer than incandescent bulbs. Their long lifetime is due to the chemical interactions between the halogen gas and the tungsten filament. Tungsten-halogen lights are sometimes used on movie sets and in underwater photography. They are also used in many headlights for cars, as shown in Figure 16. Lasers From laser surgery to a laser light show, lasers have become a large part of the world in which you live. Lasers can be made with many different materials, including gases, liquids, and solids. The wavelength of the laser depends on the materials used. One of the most common is the helium-neon laser, which produces a beam of red light with a wavelength of 632 billionths of a meter.

Audio transmission

Some radio waves carry an audio signal from a radio station to a radio. However, even though these radio waves carry information that a radio uses to create sound, you cannot hear radio waves. You hear sound when your radio changes the radio wave into a sound wave.

Loudness

Some sounds are so loud that they can be painful to hear. Loudness is the human perception of sound volume and primarily depends on sound intensity. When sound waves of high intensity reach your ear, they cause your eardrum to move back and forth a greater distance than when sound waves of low intensity reach your ear. As a result, you hear a loud sound.

Density and sound speed

Sound usually travels fastest in solids and slowest in gases. One reason for this is that the individual particles that make up liquids and solids are usually closer together than the particles that make up gases. You can understand why solids and liquids transmit sound well by picturing a large group of people standing in a line. Imagine that they are passing a bucket from person to person. If everyone stands far apart, each person has to walk a long distance to transfer the bucket, as in the left photo of Figure 3. However, if everyone stands close together, as in the right photo of Figure 3, the bucket quickly moves down the line. The people standing close to each other are like the particles that make up solids and liquids. Those standing far apart are like the particles that make up gases. When the particles that make up a medium are farther apart, sound travels more slowly through that medium.

Sound waves

Sound waves are longitudinal waves. When a noise is made, such as when a locker door slams shut, nearby molecules in the air are pushed together by the vibrations caused by the slamming door. The molecules in the air are squeezed together similar to the coils in the coiled spring toy in Figure 5. These compressions travel through the air to make a sound wave. The sizes of a sound wave's compressions, as well as the distances between those compressions, determines the nature of that sound. Sound waves in liquids and solids Sound waves can also travel through liquids and solids, such as water and wood. Particles in these mediums are pushed together and move apart as the sound waves travel through them

Human hearing involves four stages:

Stage 1: Ear gathers compressional waves which vibrate a tough membrane called: eardrum. Stage 2: The middle ear has three bones called: hammer, anvil, and stirrup which amplify sound waves. Stage 3: The inner ear contains the cochlea which vibrates sending auditory nerves. Stage 4: Brain decodes and inerprets nerve impulses.

Acoustics

Study of sound (Concert hall, engineers)

Mechanical Wave

Such as sound waves are waves that can only travel through matter. Can be either transverse or longitudinal waves.

Real images

The image that is diagrammed in Figure 5 is not virtual. Rays of light pass through the location of the image. A real image is an image that is formed when light rays converge to form the image. You could hold a sheet of paper at the location of a real image and see the image projected on the paper

Sound Quality

Suppose your friend played a note on a flute and then a note of the same pitch and loudness on a piano. Even if you closed your eyes, you could tell the difference between the two instruments. Their sounds would not be the same. Each of these instruments has a unique sound quality. Sound quality describes the differences between sounds of the same pitch and loudness. Sound quality results from overtones. Reading Check Compare sound quality and pitch. Overtones You might think that a musical instrument vibrates at only one frequency when you play only one note on that instrument. In fact, a musical instrument vibrates at many different frequencies when you play it, even when you play just one note. The lowest of these frequencies is called the fundamental frequency. On a guitar, for example, the fundamental frequency is produced by the entire string vibrating back and forth, as shown in Figure 13. The fundamental frequency primarily determines the pitch of the note that you hear. The other frequencies are called overtones. An overtone is a vibration whose frequency is a multiple of the fundamental frequency. Overtones determine the sound quality of the note that you hear. The first two guitar-string overtones are also shown in Figure 13. Consider the example of your friend playing the same note on a flute and on a piano again. Your friend produces the same fundamental frequency on both instruments. However, the loudness of each overtone differs between the two instruments.

Global Positioning System (GPS)

System of satellites, ground stations and receivers that receive high frequency microwaves signals, amplify it and return it

Sonar

System that uses the reflection of underwater sound waves to detect objects (fishing boats)

Speed of sound depends on?

Temperature and state of medium

Coherent and incoherent light

The beams from a laser light do not spread out because laser light is coherent. Coherent light is light of only one wavelength that travels in one direction with a constant distance between the corresponding crests of the waves. This is illustrated in Figure 18. Notice that the coherent waves combine to form a wave with constant wavelength and frequency. The light from an ordinary lightbulb is incoherent. Incoherent light can have more than one wavelength, can travel in more than one direction, and does not travel with a constant distance between the corresponding crests of the waves. This is also illustrated in Figure 18. The waves do not travel in the same direction, so the beam spreads out and the energy carried by the light waves is spread over a large area. Using lasers A laser beam does not spread out as it travels over long distances. Therefore, it can apply large amounts of energy to small areas. Videodisc players, surgical tools, and many other useful devices take advantage of this property. In industry, powerful lasers are used for cutting and welding materials. Surveyors and builders use lasers for measuring distances and for leveling. In communications, information can be coded in pulses of light from lasers. Lasers in medicine In the eye and in other parts of the body, surgeons can use lasers in place of scalpels to cut through body tissues. Lasers are routinely used to remove cataracts, reshape the cornea, and repair the retina. The energy from the laser seals blood vessels in the incision and reduces bleeding. Most lasers do not penetrate deeply through the skin, so they can be used to remove small tumors or birthmarks on the surface without damaging deeper tissues. CDs and videodiscs CDs and videodiscs are plastic discs with reflective surfaces that are used to store sound, images, and text in digital form. When a disc is produced, the information is burned into the surface of the disc with a laser. The laser creates millions of tiny pits in a spiral pattern that start at the center of the disc and move out to the edge. A videodisc or CD player also uses a laser to read the disc. As illustrated in Figure 19, as the laser beam strikes a pit or flat spot, different amounts of light are reflected to a light sensor. The reflected light is converted to an electric signal that can be converted into sound or images.

Waves and Particles

The difference between a wave and a particle might seem obvious—a wave is a disturbance that carries energy, and a particle is a piece of matter. However, in reality, the difference is not so clear. Waves as particles In 1887, Heinrich Hertz found that he could create a spark by shining light on a metal. (Today, we know that this spark means that electrons were ejected from the metal.) Hertz found that whether sparks occurred depended on the frequency of the light and not the amplitude. Because the energy carried by a sound wave or water wave depends on its amplitude and not its frequency, this result was mysterious. In 1905, Albert Einstein provided an explanation. An electromagnetic wave can behave as a particle called a photon. A photon is a massless bundle of energy that behaves like a particle. The photon's energy depends on the frequency of the wave. The photon's energy increases as the wave's frequency increases.

Mirror images

The different shapes of plane, concave, and convex mirrors cause them to reflect light in distinct ways. For example, concave mirrors are the only mirrors that magnify images. Convex mirrors always make objects appear to be smaller and farther away than they actually are. Each type of mirror has different uses. Most wall mirrors are plane mirrors. Most makeup and shaving mirrors are concave mirrors. Most store security mirrors are convex mirrors. Table 1 summarizes the characteristics of plane mirrors, concave mirrors, and convex mirrors.

Wavelength (Transverse and Longitudinal Wave)

The distance between one point on a wave and the nearest point just like it. For transverse waves the wavelength is from trough to trough or crest to crest. The two distances are equal on a transverse wave. On a longitudinal wave it is the distance from the middle of one compression to the middle of the next compression. It is also the distance from the middle of one rarefraction to the middle of the next rarefaction. The two are equal.

What is the electromagnetic spectrum

The entire range of electromagnetic wave frequencies.

Broadcasting radio waves

The modified carrier wave is converted from an electric signal to a radio wave by using an antenna, like the one in Figure 20. The electric signal causes electrons in the antenna to vibrate. These vibrating electrons create electromagnetic waves that travel outward from the antenna in all directions. The signal from the radio station is strongest closer to the broadcasting antenna and becomes weaker as you move away. Eventually, the signal will be too weak to be detected by your radio. This is why radios in New York City do not pick up FM radio stations broadcast in Los Angeles. Bad weather, surrounding mountains, and artificial structures can also interfere with radio transmissions.

Frequency of electromagnetic wave is

The number of vibration per second (Hz)

The speed of sound

The speed of a sound wave through a medium depends on that medium's composition and whether that medium is solid, liquid, or gas. Table 1 shows the speed of sound through some common mediums. The temperature, density, and elasticity of the medium also affect the speed of sound. Temperature and sound speed The speed of sound through a fluid depends on the temperature of that fluid. This relationship is particularly pronounced for gases but also exists for liquids, such as water. As the temperature of a fluid increases, the particles that make up that fluid move faster. This makes them more likely to collide with each other. If the particles that make up a medium collide more often, more energy can be transferred in a shorter amount of time. As a result, the sound waves travel faster

Forming images with convex lenses

The type of image that a convex lens forms depends on where the object is relative to the focal point of the lens. If an object is more than two focal lengths from the lens, as in the top panel of Figure 10, the image is real, reduced, inverted, and on the opposite side of the lens from the object. As the object moves closer to the lens, the image gets larger. The middle panel of Figure 10 shows the image formed when the object is between one and two focal lengths from the lens. Now the image is larger than the object but is still inverted. When an object is less than one focal length from the lens, as shown in the bottom panel of Figure 10, the image becomes an enlarged, virtual image. The image is virtual because the light rays from the object are not converging after they have passed through the lens. When you use a magnifying glass, you move a convex lens so that it is less than one focal length from an object. This causes the image of the object to be magnified

Properties of Electromagnetic Waves

The vibrating electric and magnetic fields of an electromagnetic wave are perpendicular to each other. That is, they are at right angles (90°) to each other. They travel outward from the moving charge, as shown in Figure 3. Because the electric and magnetic fields vibrate at right angles to the direction the wave travels, an electromagnetic wave is a transverse wave. Speed In a vacuum, all electromagnetic waves travel at 300,000 km/s. Because light is a type of electromagnetic wave, the speed of electromagnetic waves in a vacuum is usually called the "speed of light." The speed of light is nature's speed limit—nothing travels faster than the speed of light. The speed of an electromagnetic wave in matter depends on the material through which the wave travels. However, it is always slower than the speed of light in a vacuum. In matter, electromagnetic waves are usually the slowest in solids and faster in gases. Table 1 in Figure 4 lists the speed of electromagnetic waves in a vacuum and several common materials. Figure 4 illustrates that light travels slower and refracts when it enters glass.

Neon Lights

The vivid, glowing colors of neon lights, such as the one shown in Figure 15, make them a popular choice for signs and eye-catching decorations on buildings. These lighting devices are glass tubes filled with gas—often neon—and work similarly to fluorescent lights. When there is an electric current through the tube, electrons collide with the gas molecules. In this case, however, the gas molecules emit visible light. If the tube contains only neon, the light is bright red-orange. Other gases and phosphor coatings are used to make other colors.

What are electromagnetic wave

They are made by vibrating electric charges and travel through space

Visible Light

Visible light is the range of electromagnetic waves that you detect with your eyes. Visible light differs from radio waves, microwaves, and infrared waves only by its frequency and wavelength. Visible light has wavelengths around 700-billionths to 400-billionths of a meter. Color is the brain's interpretation of the wavelengths of the light absorbed by substances in the eye. These colors range from short-wavelength violet to long wavelength red, as illustrated in Figure 12. If all colors of light are present in the same place, you see the light as white.

Waves in Matter

Waves are produced by something that vibrates, and they carry energy from one place to another. Look at the water wave and the sound wave in Figure 1. Both waves are moving through matter. The water wave is moving through water, and the sound wave is moving through air. These waves travel because energy is transferred from particle to particle. Without matter to transfer the energy, these waves cannot move. However, there is another type of wave that does not require matter to transfer energy.

Both refraction and diffraction cause

Waves to bend, however, refraction occurs when waves pass through an object while diffraction occurs when waves pass around an object.

Filtering Colors

Wearing tinted glasses changes the color of almost everything that you see. If the lenses are yellow, the world takes on a golden glow. If they are rose-colored, everything looks rosy. Something similar would occur if you placed a colored, transparent plastic sheet over this white page. The paper would appear to be the same color as the plastic. The plastic sheet and the tinted lenses are filters. A filter is a transparent material that selectively transmits light. For example, color filters transmit one or more colors of light but absorb all others. The color of a filter is the color of the light that it transmits. Figure 11 shows what happens when you look at a colored object through various colored filters. On the left of Figure 11, a blue bowl looks blue because it primarily reflects blue light and absorbs more of the other colors of light. If you look at the bowl through a blue filter as in the center of Figure 11, the bowl still looks blue because the filter transmits the reflected blue light. The right image of Figure 11 shows how the bowl looks when you examine it through a red filter.

Eyesight and Lenses

What determines how well you can see the words on this page? If you do not need eyeglasses, the structure of your eye gives you the ability to focus on these words and on other objects around you. Look at Figure 12. Light enters your eye through a transparent covering on your eyeball called the cornea (KOR nee uh). The cornea causes light rays to bend so that they converge. Reading Check Describe the function of the cornea. After passing through the cornea, the light then passes through an opening called the pupil. Behind the pupil is a flexible, convex lens, called the eye lens. The eye lens helps focus light rays so that a sharp image is formed on your retina. Your retina is the inner lining of your eye, which has cells that convert the light image into electrical signals. These electric signals are then carried along the optic nerve to your brain where they can be interpreted.

What is a lens?

What do your eyes have in common with cameras and eyeglasses? Each of these things contains at least one lens. A lens is a transparent material with at least one curved surface that causes light rays to bend, or refract, as those rays pass through the lens. The image that a lens forms depends on the shape of the lens. Like curved mirrors, a lens can be convex or concave. Convex Lenses A convex lens is a lens that is thicker in the middle than at the edges. Its optical axis is an imaginary straight line that is perpendicular to the surface of the lens at its thickest point. When light rays approach a convex lens traveling parallel to its optical axis, the rays are refracted toward the center of the lens, as shown in Figure 9. All light rays traveling parallel to the optical axis in Figure 9 are refracted so they pass through a single point, which is the focal point of the lens. The focal length of the lens depends on the shape of the lens. If the sides of a convex lens are less curved, light rays are bent less. As a result, lenses with flatter sides have longer focal lengths. Figure 9 also shows that light rays traveling along the optical axis are not bent at all.

Spotlights

What happens when you place an object exactly at the focal point of a concave mirror? Figure 6 shows that when the object is at the focal point, the mirror reflects all light rays parallel to the optical axis. The rays never meet, and no image forms. Even the virtual rays that extend behind the mirror do not meet. Therefore, a light placed at the focal point is reflected in a beam. Car headlights, flashlights, spotlights, and other devices use concave mirrors in this way to produce light beams with nearly parallel rays

Refraction of Light

What occurs when a light wave passes from one material to another—from air to water, for example? Light rays refract, or bend. Refraction is caused by a change in the speed of a wave when it passes from one material to another. If the light wave is traveling at an angle other than 90° to the boundary between the materials and the speed that light travels is different in the two materials, then the wave will bend. If light hits a boundary at 90°, it will change speed but not bend. Reading Check Identify when refraction occurs. The index of refraction The amount of bending depends on the speed of light in each material. The greater the difference in speeds, the more the light is bent as it crosses the boundary at an angle. Every material has an index of refraction. The index of refraction is a property of a material that indicates how much the speed of light in the material is reduced compared to the speed of light in a vacuum. In most materials, the index of refraction also depends on the light's wavelength. Longer wavelengths have smaller indices of refraction. The larger the index of refraction, the slower the speed of light will be in the material. For example, because glass has a larger index of refraction than air, light moves more slowly in glass than in air. Many useful devices, such as eyeglasses, binoculars, cameras, and microscopes, form images by using glass lenses to refract light

Making electromagnetic waves

When an electric charge vibrates, the electric field around it changes. Because the electric charge is in motion, it also has a magnetic field around it. This magnetic field also changes as the charge vibrates. As a result, the vibrating electric charge is surrounded by a changing electric field and a changing magnetic field. How do the vibrating electric field and magnetic field around the charge become a wave that travels through space? The changing electric field around the charge creates a changing magnetic field. This changing magnetic field then creates a changing electric field. This process continues, with the magnetic field and electric field continually creating each other

Acoustics

When an orchestra stops playing, does it seem as if the sound of its music lingers for a couple of seconds? The sounds and their reflections reach your ears at different times, so you hear echoes. This echoing effect produced by many reflections of sound is called reverberation (re vur bu RAY shun). During an orchestra performance, reverberation can ruin the sound of the music. To prevent this problem, the people who design concert halls must understand how the size, shape, and furnishings of the room affect the reflection of sound waves. These scientists and engineers specialize in acoustics (uh KEWS tihks). Acoustics is the study of sound. People who study acoustics know that soft, porous materials, such as curtains, can reduce excess reverberation. Figure 19 shows a concert hall that has been designed to produce a good listening environment.

Optical Fibers

When laser light must travel long distances or be sent into hard-to-reach places, optical fibers often are used. These transparent glass fibers transmit light from one place to another by a process called total internal reflection. Partial Reflection Remember that refraction can happen when light changes speed as it travels from one medium to another. When light travels from water to air, it speeds up and the direction of the light ray is bent away from the normal, as shown in Figure 22. However, not all the light passes through the surface. Some light is reflected back into the water. As the underwater light ray makes larger angles with the normal, the refracted light rays in the air bend closer to the surface of the water. Additionally, more light is reflected back into the water. At a certain angle, called the critical angle, the refracted ray has been bent so that it is traveling along the surface of the water, as shown in Figure 22. For a light ray traveling from water into air, the critical angle is about 49°. Total Internal Reflection Figure 22 also shows what happens if the underwater light ray strikes the boundary between the air and water at an angle larger than the critical angle. There is no longer any refraction, and the light ray does not travel in the air. Instead, the light ray is reflected at the boundary, just as if a mirror were there. This complete reflection of light at the boundary between two different materials is called total internal reflection. The light wave follows the law of reflection. For total internal reflection to occur, light must travel slower in the first medium and must strike the boundary at an angle that is greater than the critical angle.

Water waves

When the wind blows across the surface of the ocean, water waves form. Water waves are often thought of as transverse waves, but this is not entirely correct. The water in water waves does move up and down as the waves go by. But the water also moves short distances back and forth along the direction that the wave is traveling. This movement happens because the low part of the wave can be formed only by pushing water forward or backward toward the high part of the wave, as shown on the left in Figure 4. This is much like a child pushing sand into a pile. Sand must be pushed in from the sides to make the pile. As the wave passes, the water that was pushed aside moves back to its initial position, as shown on the right in

Interference

When two or more waves overlap to form a new wave. Suppose two waves travel toward each other on a long rope as in the top panel of Figure 21. What happens when the two waves meet? The two waves pass through each other, and each one continues to travel in its original direction, as shown in the middle and bottom panels of Figure 21. However, when the waves meet in the middle panel of Figure 21, they form a new wave that looks different from either of the original waves. When two waves arrive at the same place at the same time, they combine to form a new wave. Interference is the process of two or more waves overlapping and combining to form a new wave. This new wave exists only while the two original waves continue to overlap. Two waves can combine through either constructive interference or destructive interference. Constructive interference In constructive interference, as shown in the top panel of Figure 22, the waves add together. This happens when the crests of two or more transverse waves arrive at the same place at the same time and overlap. The amplitude of the new wave that forms is equal to the sum of the amplitudes of the original waves. Constructive interference also occurs when the compressions of different longitudinal waves overlap. If the waves are sound waves, for example, constructive interference produces a louder sound. Waves undergoing constructive interference are said to be in phase. Destructive interference In destructive interference, the waves subtract from each other as they overlap. This happens when the crests of one transverse wave meet the troughs of another transverse wave, as shown in the bottom panel of Figure 22. The amplitude of the new wave is the difference between the amplitudes of the waves that overlapped. With longitudinal waves, destructive interference occurs when the compression of one wave overlaps with the rarefaction of another wave. One way to think of this is that the compressions of one wave "fill in" the rarefactions of another wave. Th compressions and rarefactions combine and form a wave with reduced amplitude. When destructive interference happens with sound waves, it causes a decrease in loudness. Waves undergoing destructive interference are said to be out of phase.

Diffraction

When waves strike an object, several things can happen. The waves can be reflected. If the object is transparent, light waves can be refracted as they pass through it. Often, some waves are reflected and some waves are refracted. If you look into a glass window, sometimes you can see your reflection in the window, as well as objects behind it. Light is passing through the window and is also being reflected at its surface. Waves can also behave another way when they strike an object. The waves can bend around the object. Figure 18 shows ocean waves changing direction and bending after they strike an island. Diffraction is the bending of a wave around an object. Diffraction and refraction both cause waves to bend. The difference is that refraction occurs when waves pass through an object, while diffraction occurs when waves pass around an object. All waves, including water waves, sound waves, and light waves, can be diffracted. Less diffraction occurs if the wavelength is smaller than the obstacle. More diffraction occurs if the wavelength is the same size as the obstacle.

Standing waves

When you make transverse waves on a rope, you might attach one end to a fixed point, such as a doorknob, and shake the other end. The waves that you produce then reflect back from the doorknob. What happens when the incident and reflected waves meet? As the two waves travel in opposite directions along the rope, they continually pass through each other. Interference takes place as the waves from each end overlap along the rope. At any point where a crest meets a crest, a new wave with a larger amplitude forms. But at points where crests meet troughs, the waves cancel each other and no motion occurs. The interference of the two identical waves makes the rope vibrate in a special way, as shown in Figure 23. The waves create a pattern of crests and troughs that do not seem to be moving. Because the wave pattern stays in one place, it is called a standing wave. A standing wave is a special type of wave pattern that forms when waves equal in wavelength and amplitude but traveling in opposite directions continuously interfere with each other. Standing waves have nodes, which are locations where the interfering waves always cancel. The nodes always stay in the same place on the rope. Meanwhile, the wave pattern vibrates between the nodes Standing waves in music When the string of a violin is played with a bow, it vibrates and creates standing waves. The standing waves in the string help produce a rich, musical tone. Other instruments also rely on standing waves to produce music. Some instruments, such as flutes, create standing waves in a column of air. In other instruments, such as drums, a tightly stretched piece of material vibrates in a special way to create standing waves. As the material in a drum vibrates, nodes are created on the surface of the drum.

Resonance

When you were younger, you might have played on a swing like the one in Figure 24. You probably noticed that you could make the swing go higher by pumping your legs and arms. It was not necessary to pump hard, but timing was important. If you pumped in time to the swing's rhythm, you could go quite high. You can accomplish similar effects with sounds. Suppose you have a tuning fork that has a single natural frequency of 440 Hz, which means that the tuning fork naturally vibrates at 440 Hz when struck. Now think of a sound wave with a frequency of 440 Hz strikes the tuning fork. Because the sound wave has the same frequency as the natural frequency of the tuning fork, the tuning fork will begin to vibrate. Resonance is the process by which an object is made to vibrate by absorbing energy at its natural frequencies. Sometimes resonance can cause an object to absorb a large amount of energy. An object vibrates more and more strongly as it absorbs energy at its natural frequencies. If the object absorbs enough energy, it might break.

Colors

Why do some apples appear to be red, and others look green or yellow? An object's color depends on the wavelengths of light that it reflects and that our eyes detect. You know that white light is a blend of all colors of visible light. When a red apple is struck by white light, it reflects more red light than green or blue light. Figure 8 shows white light striking a green leaf. The leaf reflects more green light than other colors and appears green. Although some objects appear to be black, black is not a color that is present in visible light. Objects that are black absorb all colors of light and reflect little or no light back to your eye. White objects are white because they reflect all colors of visible light. Reading Check Explain why a white object is white. Seeing Color As you approach a busy intersection, the color of the traffic light changes from green to yellow to red. On the cross street, the color changes from red to green. How do your eyes detect the differences between red, yellow, and green light?

Convex Mirrors

Why do you think the security mirrors in banks and stores are shaped the way that they are? The next time that you are in a store, look at one of the back corners or at the end of an aisle to see if a large, rounded mirror is mounted there. You can see a large area of the store in the mirror. A convex mirror is a mirror that curves outward, like the back of a spoon. Light rays that hit a convex mirror spread apart after they are reflected. Look at Figure 8 to see how the rays from an object are reflected off a convex mirror to form an image. The reflected rays diverge and never meet, so the image formed by a convex mirror is a virtual image. The image is also always upright and is smaller than the actual object. Reading Check Describe the image formed by a convex mirror. Uses of convex mirrors Because convex mirrors cause light rays to diverge, they allow large areas to be viewed. As a result, a convex mirror is said to have a wide field of view. In addition to increasing the field of view in places like grocery stores and factories, convex mirrors can widen the view of traffic that can be seen in rear-view or side-view mirrors of automobiles. However, because the image that a convex mirror forms is smaller than the object, your perception of distance can be distorted. Objects look farther away than they truly are in a convex mirror. Distances and sizes seen in a convex mirror are not realistic, so most convex side mirrors on cars carry a printed warning that states "Objects in mirror are closer than they appear."

Interpreting color

Why does a banana appear to be yellow? The light reflected by the banana causes the cone cells that are sensitive to red and green light to send signals to your brain. Your brain would get the same signal if a mixture of red light and green light reached your eye. Again, your red and green cones would respond, and you would see yellow light because your brain cannot perceive the difference between incoming yellow light and yellow light produced by combining red and green light. The next time that you are at a play or a concert, look at the lighting above the stage. Observe how the colored lights combine to produce effects onstage.

Cameras

With the click of a button, you can capture a beautiful scene in a photo. How does a digital camera make a reduced image of a life-sized scene? Figure 21 shows the path that light follows as it enters a camera from a distant object. The light rays from distant objects are almost parallel to each other. When you take a picture with a camera, a shutter opens to allow light to enter the camera for a specific length of time. The light reflected off the object enters the camera through an opening called the aperture. The camera lens focuses the image onto an image sensor, which converts light into electric signals. A computer then processes these signals into an image that can be displayed on a screen or printed.

Polarized Light

You can make transverse waves in a rope vibrate in any direction—horizontal, vertical, or anywhere in between. Light also is a transverse wave and can vibrate in any direction. The direction of vibration for a light wave refers to the direction that its electric or magnetic field vibrates. Linearly polarized light is light with a magnetic field that vibrates in only one direction. As always, the electric field is perpendicular to the magnetic field. Polarizing filters Light can be polarized by using a special filter with lines of crystals that act like a group of parallel slits. Only light waves with magnetic fields that vibrate in the same direction as the lines of crystals can pass through. This is similar to the rope wave traveling through the fence in Figure 20. Polarized lenses When light is reflected from a horizontal surface, such as a lake, some of the light is polarized with its magnetic field vibrating vertically. The lenses of polarizing sunglasses are polarizing filters that block the reflected light with vertically vibrating magnetic fields, thus reducing glare.

Virtual images

You can understand your brain's interpretation of your reflection in a mirror by looking at Figure 3. The light waves that are reflected off you travel in all directions. Light rays reflected from your chin strike the mirror at different places. Then, they reflect off the mirror in different directions. A few of these light rays reflect off the mirror in just the right way to enter your eyes. Recall that your brain always interprets light rays as if they have traveled in a straight line. It does not realize that the light rays have been reflected and that they changed direction. Your reflected image appears to be behind the mirror. An image that your brain perceives even though no light rays pass through the location of that image is a virtual image. The imaginary light rays that appear to come from virtual images are called virtual rays. The dashed line in Figure 3 is a virtual ray. Plane mirrors always form upright, virtual images.

Telescopes

You know from your experience that it is difficult to see faraway objects clearly. When you look at an object, only some of the light reflected from its surface enters your eyes. As you move farther away from the object, the amount of light entering your eyes decreases, as shown in Figure 16. As a result, the object appears dimmer and less detailed. A telescope uses a lens or a concave mirror that is much larger than your eye to gather more of the light from distant objects. The largest telescopes can gather more than a million times more light than the human eye. As a result, objects such as distant galaxies appear much brighter. Because the image formed by a telescope is so much brighter, more detail can be seen when the image is magnified.

Mirages

You might have seen what looks like the reflection of an oncoming car in a pool of water on the road ahead. As you get closer, the water seems to disappear. You saw a mirage, an image of a distant object produced by the refraction of light through air layers of different densities. Mirages, such as those shown in Figure 7, occur when the air at ground level is much warmer or cooler than the air above it. The density of air increases as air cools. Light waves travel slower as the density of air increases, so light travels slower in cooler air. As a result, light waves refract as they pass through air layers with different temperatures. These refracted light waves form additional images of objects

The Ear

Your ears and brain work together to interpret sound waves. When you think of your ear, you probably picture just the fleshy, visible, outer part. But, as shown in Figure 4, the human ear has three sections called the outer ear, the middle ear, and the inner ear. Each section of the ear has a different function. The outer ear The visible part of your ear, the ear canal, and the eardrum make up the outer ear. The outer ear gathers sound waves. The gathering process starts with the outer part of your ear, which is shaped to help capture and direct sound waves into the ear canal. The ear canal is a passageway that is 2-cm to 3-cm long and is a little narrower than your index finger. The sound waves travel along this passageway, which leads to the eardrum. The eardrum is a tough membrane about 0.1 mm thick that transmits sound from the outer ear to the middle ear. Reading Check Identify what makes the eardrum vibrate. The middle ear When the eardrum vibrates, it passes the sound waves into the middle ear, where three tiny bones start to vibrate. These bones are called the hammer, the anvil, and the stirrup. They make a lever system that increases the force and pressure exerted by the sound waves. The bones amplify the sound wave. The stirrup is connected to a membrane on a structure called the oval window, which vibrates as the stirrup vibrates. ? Inquiry Virtual Lab ? Inquiry MiniLab SC.912.P.10.21: Qualitatively describe the shift in frequency in sound or electromagnetic waves due to the relative motion of a source or a receiver. Hair cells in the human ear send nerve impulses to the brain when sound waves cause them to vibrate. In this photo, the hair cells are magnified 5,500 times. The inner ear When the membrane in the oval window vibrates, the sound vibrations are transmitted into the inner ear. The inner ear contains the cochlea (KOH klee uh). The cochlea is a spiral-shaped structure that is filled with liquid and contains tiny hair cells. These hair cells are shown in Figure 5. When the tiny hair cells in the cochlea begin to vibrate, nerve impulses are sent through the auditory nerve to the brain. It is the cochlea that converts sound waves to nerve impulses. Hearing loss When a person's hearing is damaged, it is usually because the tiny hair cells in the cochlea are damaged or destroyed, often by loud sounds. This damage is permanent. The hair cells in the cochlea of humans and other mammals do not grow back when damaged or destroyed. However, current research suggests that doctors may be able to repair damaged or even destroyed hair cells in the future. Much of this research centers on birds. Unlike in mammals, the hair cells in birds do grow back when damaged or destroyed

Fluorescent Lights

Your school might have fluorescent (floo REH sunt) lights, like the ones shown in Figure 14. Fluorescent light is light generated by using phosphors to convert ultraviolet radiation to visible light. A phosphor is a substance that absorbs ultraviolet radiation and then emits visible light. A fluorescent bulb is filled with a gas at low pressure and is coated on the inside with phosphors. An electrode is at each end of the tube. Electrons are given off when the electrodes are connected in a circuit. These electrons collide with the gas atoms, which then emit ultraviolet radiation. The wavelength of light emitted depends on the type of gas used. The phosphors absorb this radiation and convert it to visible light.

Structure of your eye

allows you to focus on the object light enters eye through the cornea, a transparent covering on eye bal.

Which sound wave property is most related to loudness?

amplitude

Ray tracing for concave mirrors You

can diagram how concave mirrors form images by tracing some of the light rays involved. Suppose that the distance between an object, such as the candle in Figure 5, and the mirror is greater than the focal length. Light rays bounce off the candle in all directions. One light ray, labeled Ray A, starts from a point on the flame of the candle and passes through the focal point on its way to the mirror. Ray A is then reflected parallel to the optical axis. Another ray, Ray B, starts from the same point on the candle's flame, but it travels parallel to the optical axis as it moves toward the mirror. The mirror then reflects Ray B through the focal point. The place where Ray A and Ray B meet after they are reflected is a point on the reflected image of the flame. More points on the reflected image can be located in this way. From each point on the candle, one ray can be drawn that passes through the focal point and is reflected parallel to the optical axis. Another ray can be drawn that travels parallel to the optical axis and then reflects through the focal point. The point where the two rays meet is on the reflected image

Sound Quality

differences among sounds of the same pitch and loudness that's why a piano sounds different than a flute playing the same part.

Plane mirror

flat, smooth mirror in which an image appear upright

Loudness

human perception of sound intensity which is measured in decibles (db)

Ultrasound

in Medicine Ultrasonic waves are commonly used in medicine. Medical professionals use ultrasound to examine many parts of the body, including the heart, liver, gallbladder, pancreas, spleen, kidneys, breasts, and eyes. Medical professionals can also use ultrasonic imaging, which is much safer than X-ray imaging, to monitor a human fetus. When ultrasound is used for medical imaging, an ultrasound technician directs the ultrasound waves toward a target area of a patient's body. The sound waves reflect off the targeted area, and the reflected waves are used to produce electronic signals. A computer program converts these signals into video images called sonograms. A sonogram of a human fetus is shown in Figure 22. Kidney stones and ultrasound Medical professionals can also use ultrasound to treat certain medical problems. For example, ultrasound can be used to break up kidney stones. Bursts of ultrasound create vibrations that cause the stones to break into small pieces. These fragments then pass out of the body with the urine. Without ultrasound, surgery would be necessary to remove the kidney stones

Music

made of sound that are deliberately used in a regular pattern

electromagnetic waves with wavelengths between 0.1 mm and 30 cm electromagnetic waves with wavelengths from about 400-billionths to 10-billionths of a meter electromagnetic waves between about 10-billionths of a meter and 1-trillionths of a meter electromagnetic waves shorter than about 100-trillionths of a meter electromagnetic waves with wavelengths longer than 10 cm electromagnetic waves with wavelengths between about 1-thousanth meter and about 700-billionths of a meter

microwave, ultraviolet waves, x-rays, gamma rays, radio rays, infrared rays

Convex mirror

mirror curved outward, diverge light rays when reflected and show virtual images

What does a sound's frequency most influence?

pitch

Instruments use

resonators or hollow chambers that amplify sound when the air inside vibrates. Ex: brass + woodwinds, mouthpiece, guitars + violins, hollow body, drums

Concave mirror

the mirror surface is curved inward, image depends on location of objective to focal point

Lens

transparent material with a curved surface that reflects light rays

Telescope

use mirrors and lenses to gather more light from far away objects than the eye does

Microscropes

uses two convex lenses with short focal lengths to magnify small, close objects

Section Summary

◗ Incandescent and fluorescent lightbulbs are often used in homes, schools, and offices. ◗ When electrons collide with neon gas, red light is emitted. ◗ A tungsten-halogen bulb is brighter and hotter than an ordinary incandescent bulb. ◗ Lasers emit narrow beams of coherent light.

Section Summary

◗ Refracting telescopes use two convex lenses to gather and focus light. ◗ Reflecting telescopes use a concave mirror, a plane mirror, and a convex lens to collect, reflect, and focus light. ◗ Placing a telescope in orbit avoids the distorting effects of Earth's atmosphere. ◗ A microscope uses two convex lenses with short focal lengths to magnify small, close objects. ◗ A camera lens focuses light onto an image sensor.

Section Summary

◗ The color of an object depends on the wavelengths of light it reflects. ◗ Rod and cone cells are light-sensitive cells found in the human eye. ◗ The color of a filter is the color of the light that the filter transmits. ◗ All light colors can be created by mixing the primary light colors—red, green, and blue. ◗ All pigment colors can be formed by mixing the primary pigment colors—magenta, cyan, and yellow.

Section Summary

◗ The magnetic fields in linearly polarized light vibrate in only one direction. ◗ Polarizing filters transmit light polarized in one direction. ◗ Lasers are used to produce holograms. ◗ The complete reflection of light at the boundary between two materials is called total internal reflection.