Physics unit 6 quiz review

What is the range of the visible spectrum from shortest to longest wavelength?

400 (violet) - 700 nm (red)

What are examples of additive color mixing? Subtractive color mixing?

Additive color mixing applies to light and our eyes. Subtractive color mixing happens with colored pigments, inks, and dyes.

Ultrasonic frequencies

frequencies HIGHER than 20,000 Hz

Infrasonic frequencies

frequencies LOWER than 20 Hz

Diffraction

Diffraction is the bending of wave fronts into an open part of a medium and around corners of barriers. We saw a mechanical wave example of this in the ripple tank experiment #3. In sound waves, hearing someone around a corner is an example of diffraction. In light waves, light diffracts around clouds, creating some very cool patterns!

What is a beat frequency? Why is the pattern of beats produced?

A beat frequency is produced by sound wave interference. Repeating patterns of constructive and destructive interference when two sources have different frequencies create a pattern of loud and soft "beats." The number of beats per second is called the beat frequency and is equal to the difference in frequency of the two sources.

What is a standing wave and how is it created? What are nodes and anti-nodes?

A standing wave is created when a wave reflects back on itself. Constructive interference creates areas of maximum displacement called anti-nodes and destructive interference created nodes which remain stationary.

Absorption

Absorption occurs when part or all of a wave is blocked by a barrier. This occurs in sound proofing for some frequencies of sound. In light, an example would be subtractive color mixing; i.e. - a red rose absorbs all frequencies of light except for red.

What is an EM Wave? What is the Electromagnetic Spectrum? How is it laid out in terms of frequency, wavelength, and energy?

An electromagnetic wave is a caused by simultaneous oscillations in the electric and magnetic fields. It is a 2 dimensional transverse wave. The EM spectrum organizes different types of EM waves from longest to shortest wavelengths. Waves are also arranged in order from lowest to highest energy and frequencies.

What is the relationship between energy and frequency for a photon?

As the energy of a photon increases, its frequency increases as well.

Is black a color of light? Why or why not?

Black is a lack of color/light! Thus it is not a color at all.

If frequency changes, what other wave properties are changed? Are they directly or indirectly related?

If frequency changes (and the medium is not), the period changes inversely (i.e. - if frequency increases, period decreases), as does the wavelength (also inversely).

Interference

Interference is a result of the superposition principle which states that waves can be in the same place at the same time. Constructive interference means that a wave with larger amplitude is produced; destructive interference means that a wave with small amplitude (or even 0!) is produced. In sound waves, interference patterns create beat frequencies. In light waves, interference patterns in Young's double slit experiment showed that light has wave properties.

A tuning fork has a frequency of 465 Hz. When a second tuning fork is struck, beat interference patterns occur with a beat frequency of 5 Hz. What is the lowest and highest frequency of the second fork?

LOWEST FREQUENCY: 465Hz - 5Hz = 460 Hz HIGHEST FREQUENCY: 465Hz + 5Hz= 470 Hz

Is white a color of light? Why or why not?

NO! White light is the presence of all color of the visible spectrum

How can we use prisms to prove white light is made up of all the visible colors of light? What is dispersion?

Prisms break white light into the visible spectrum. They do this using refraction and dispersion. Dispersion is a phenomenon in which the angle of refraction depends on the wavelength of light. This means that different colors of light bend at different angles, thus creating the visible spectrum.

What colors do we typically say make up the visible spectrum?

ROYGBIV

Reflection

Reflection is the redirection of waves back into the same part of the medium they came from as a result of interaction with a barrier or medium change. In sound, this can be seen with echoes. In light, spectral reflection, such as with a mirror, reflects light rays parallel to each other. In diffuse reflection, light is scattered and thus has a halo of light, rather than a beam.

Refreaction

Refraction is the bending of waves when they enter a new medium. We saw a mechanical wave example of this in the ripple tank experiment #2. In sound, we experience refraction with different temperatures of air. In light, we see refraction when mediums are changed according to Snell's law; this is also the reason that prisms can break white light down into the visible spectrum.

Explain Snell's Law and index of refraction.

Snell's law is the law of refraction for light waves. The index of refraction is a property of a medium that affects the angle of refraction.

Why are sunsets red? Why is the sky blue?

Sunsets are red because red wavelengths of light survive being scattered by the air before reaching our eyes. The sky is blue because blue wavelengths of light are scattered by the air molecules, so when we look up, we see all the scattered blue light!

Define the Doppler Effect

The Doppler Shift is the APPARENT shift in frequency/wavelength due to the relative motion of a sound source to an observer.

Anvil

The anvil is a small bone in the middle ear; it vibrates due to vibrations from the hammer bone

What color is a yellow ball when viewed under cyan light?

The ball is yellow because of subtractive color mixing: blue light is subtracted/absorbed. We see yellow light because of additive color mixing: green and red light are reflected. Cyan light is a mixture of blue and green light; since blue is absorbed, we will see the ball as GREEN.

Cochlea

The cochlea has tiny hairs connected to nerve receptors. These hairs vibrate due to the pressure wave created by the bones in the middle ear. These hairs create electrical impulses that are sent to the brain and interpreted as sound!

What is the critical angle and how does it relate to total internal reflection?

The critical angle is the angle of incidence in the more optically dense medium at which the angle of refraction in the less optically dense medium is exactly 90°. If the incident angle of an incoming light beam is greater than the critical angle, total internal reflection will occur.

Eardrum

The eardrum vibrates when sound waves reach it; these vibrations are then carried as pressure waves to the middle ear

Hammer

The hammer is a small bone in the middle ear; it vibrates due to pressure waves from the eardrum.

Frequency

The number of complete cycles that pass a fixed point every second; units: Hertz (Hz)

What are the primary, secondary, and complementary colors of light?

The primary colors of light are red, blue, and green. The secondary colors of light are cyan, yellow, and magenta. The complementary colors are blue and yellow; green and magenta; & red and cyan.

What are the primary and secondary colors of ink/pigment?

The primary colors of pigment/ink are cyan, yellow, and magenta. The secondary colors of pigment/ink are red, blue, and green.

What is the speed of light? If it is constant, why does it sometimes seem to change with the medium?

The speed of light is constant: c = 3.00 x 108 m/s. Sometimes it seems slower in a medium because it has to take a longer path to get through the medium. The denser a medium is, the more the light will bounce around while passing through it

Stirrup

The stirrup is a small bone in the middle ear; it vibrates due to vibrations from the anvil bone. It then transmits pressure waves to the inner ear

If you shine a red flashlight and a blue flashlight at a white wall, what color will you see where the flashlight beams overlap?

This is additive color mixing: red + blue = MAGENTA light

Total internal refraction

Total internal reflection occurs when light falls on a surface of a less optically dense medium at an angle of incidence equal to or greater than the critical angle of the substance. There is no refracted ray; occurs at critical angle.

Transmission

Transmission occurs when some or all waves pass through a material. We saw a mechanical wave example of this in the ripple tank demo #2. An example from sound would be hearing voices from a neighboring room through the wall. An example from light would be light passing through tissue paper.

How does the apparent frequency for sound waves shift for an observer based on the motion of the source? How does this differ from the Doppler Effect for light waves?

When a sound source is moving TOWARDS the observer, the pitch the observer hears will be HIGHER than the source frequency and vice versa! When a light source is moving TOWARDS the observer, the wavelength the observer sees will be SHORTER than the source frequency, thus the light is BLUE SHIFTED; and vice versa!

Supersonic speeds

speeds FASTER than the speed of sound

Subsonic speeds

speeds SLOWER than the speed of sound (~343 m/s)