Physics B WAVES (some of the answers)
In an experiment, a ringing bell is placed in a vacuum jar that does not have any air in it. What best describes why the bell is seen vibrating but not heard?
Light does not need a medium to travel through, but since sound waves must have a medium to vibrate, sound is not created where no air is present.
a __________ is a point on a standing wave that appears to be stationary.
NODE
The figure shows a sound wave as a function of time when the source is stationary with respect to the observer.
NOT A NOT C
Color is a result of the absorption and reflection of light. A shirt appears a color because it reflects that color of light. A shirt appears black when it absorbs all wavelengths of light.
NOT The light is transmitted through the shirt, so no color appears. NOT The shirt absorbs the sunlight, so it appears white.
The appearance of color is a result of the absorption and reflection of certain wavelengths of light. A shirt appears a certain color because it reflects that color of light. On the other hand, a shirt appears black when it absorbs all wavelengths of light and white when it reflects all wavelengths of light.
NOT The temperature of the shirt will depend on how much sunlight is diffracted around the shirt.
Rohit is trying to tune an instrument. He strikes a tuning fork and then plays a note that almost matches it. Rohit hears the volume of the two waves beating, which sounds like "wah-wah-wah-wah."
NOT The two waves produced have different amplitudes
The table lists information about four devices.
NOT W, X, Y, Z
A wire has a current that flows to the right.
NOT circles around the wire that go in at the top
In 1940, the Tacoma Narrows Bridge across the Puget Sound collapsed. The bridge was a suspension bridge. The wind blowing through the narrows matched the natural frequency of the bridge. This resulted in a large movement of roadway, which eventually caused the bridge to fail.
NOT interference, because destructive interference occurred when the wind frequency matched the natural frequency of the bridge
A source emits a sound and is represented by the red dot in this map. Four people are located around the source, and the circles represent the sound wave.
NOT person B
A marching band is practicing. The band director sees the drum major hit a drum. How far away is the director if he hears the drumbeat in 0.40 seconds? The speed of sound is 330 m/s.
132 m
An incident ray of light strikes a diamond at an angle of 45°. The index of refraction of air is 1.0003 and the index of refraction of a diamond is 2.42.
17°
A frequency generator sends a 550 Hz sound wave through both water and ice.
3.1 m
An FM radio station broadcasts at 9.23 × 107 Hz. Given that the radio waves travel at 3.00 × 108 m/s, what is the wavelength of these waves?
3.25 m
Ultraviolet light from a distant star is traveling at 3.0 × 108 m/s. How long will it take for the light to reach Earth if it must travel 4.0 × 1016 km?
3.7 × 104 hours
A car's horn produces a constant frequency of 350 Hz as it passes by Suzy. What is the best estimate of the frequency Suzy hears after the car passes her?
330 Hz
A flute plays a note with a frequency of 266 Hz. What is the speed of sound if the wavelength is 1.3 m?
346 m/s
Violet light has a frequency of 7.26 × 1014 Hz and travels at a speed of 3.00 × 108 m/s.
413
This diagram shows how loud certain frequencies must be in order for people of different ages to hear them. The needed intensity is called the "hearing level."
65
The transverse wave shown has a wavelength of 1.5 m and is traveling in the x-direction.
8.0 seconds
A sound with an intensity greater than _____ dB can cause damage to human ears.
85
The diagrams show the sound waves produced in one second from various tuning forks.
A
The two waves in the diagram are occupying the same place at the same time. Which diagram shows the resulting interference?
A
Which diagram best shows the perceived sound wave heard by a woman after a police car has passed her?
A
Four compasses are placed around a wire, as shown.
A current does not flow in the wire.
Which is the best example of the wave phenomenon called transmission?
A street is seen through a window.
A transverse wave is shown.
A transverse wave is shown.
A wave is produced in a Slinky as shown.
A. (the one pointing left and right)
Walt made a study chart listing uses for two types of electromagnetic waves.
A: Microwaves B: Ultraviolet Waves
If the energy of the wave becomes part of the internal energy of the object, then the wave's energy is ______
ABSORBED
Ten students stand in a circle and are told to make a transverse wave. What best describes the motion of the students?
One at a time, each student lifts his or her hands up and then down.
The subjective perception of frequency is ______
PITCH
Is the perceived frequency of a sound wave.
Pitch
Which best compares concave and plane mirrors?
Plane mirrors produce only virtual images, and concave mirrors produce real and virtual images.
A process that modifies light waves so they vibrate in a single plane is referred to as
Polarization
Incident ray X passes parallel to the principal axis of a concave lens. Incident ray Y passes parallel to the principal axis of a convex lens.
Ray X appears as though it passed through the focal point in front of the lens, and ray Y passes through the focal point on the other side of the lens.
When a DVD is played, a laser light hits the surface of the disk and then returns to the detector.
Reflection
A lens focuses light at a single point called the focal point.
Refraction
The image shows water passing through a barrier.
Refraction
A coil of wire that carries an electric current is a(n)
Solenoid
The speed of sound in ice, water, and steam is shown.
Sound travels fastest in ice because energy is easier to transfer when the molecules are close together.
Which describes the relationship between the frequency, wavelength, and speed of a wave as the wave travels through different media?
As speed changes, wavelength changes and frequency remains constant.
A longitudinal wave is shown.
B
Look at the diagram. Which point identifies a node?
B
Two wave pulses move toward each other along a rope.
B
Look at the wave diagram. Which wave would produce a standing wave when combined with the original one?
B. (the same amplitude, but opposite direction of wave motion)
________ interference occurs when two waves overlap and the resulting wave has a larger amplitude.
CONSTRUCTIVE
Interference occurs when two waves overlap and the resulting wave has a larger amplitude.
Constructive
Consider this image of a wave. Which wave would cause destructive interference at every point of the wavelength and completely cancel out the wave?
D
Which is the correct formula for finding the frequency of an electromagnetic wave?
D
These graphs show measurements of the density of air as different sound waves pass a single point.
D. (the one with the greatest amplitude)
If a soundproof door is almost shut but still leaves a small opening, what wave phenomenon is responsible for someone being able to hear sound from the room while standing by the wall to the side of the opening?
Diffraction
What is the name of the perceived change in a sound wave's frequency due to motion between the observer and the sound source?
Doppler effect
The image shows a pendulum in simple harmonic motion. The pendulum starts at A and swings to E.
E D A B
How many wavelengths are seen in this image of a sound wave?
Four
What type of wave is a microwave?
Heat
A sound wave with amplitude xo is measured by an observer to have an intensity of I0 when the observer is standing 4.0 meters from the source.
Increase the amplitude to 2xo and stand 2 meters from the source.
As the frequency of electromagnetic waves increases, what happens to the wavelength?
It decreases.
Which best describes the energy of a sound wave as it travels through a medium?
It decreases.
What best explains why a person can become sunburned by spending too much time at the beach?
Sunlight is an electromagnetic wave carrying energy that is absorbed by the skin.
Noah and Nina are 15 m apart in a closed room. Noah says the same sentence twice. The first time, Nina does not hear the sound, but she does hear the sentence the second time.
The air molecules in the compressions of the second wave are more dense.
What best describes the speed of light waves in solids, liquids, and gases?
The speed is fastest in gases.
A sound wave travels through water. What best describes the direction of the water particles?
The water particles move in the same direction as the vibrating source of the sound wave.
What do all electromagnetic waves have in common?
They can travel at the speed of light.
How are electromagnetic waves different than all other waves?
They can travel through space.
A sound wave is produced when a medium begins to _________
VIBRATE
Look at the two wave diagrams. Which best describes the difference between wave A and wave B?
Wave A has a greater pitch and frequency.
All parts of the electromagnetic spectrum travel at a speed of 3 × 108 m/s when traveling through no medium. A "vacuum" means that there is no medium, such as a tube without any air in it. Therefore, 3 × 108 m/s is said to be the speed of light in a vacuum.
Wavelength divides in half and speed stays the same.
Which best describes electromagnetic waves moving from gamma rays to radio waves along the electromagnetic spectrum?
Wavelength increases and frequency decrease.
Which accurately compares concave and convex lenses?
With concave lenses, the characteristics of the image do not depend on the placement of the object, but with convex lenses, they do.
Dierdre drew a diagram to compare the three types of mirrors.
X: Curves outward Y: Image may be smaller than object Z: Image is always virtual
The diagram shows changing wavelengths along the electromagnetic spectrum.
Y: Radio Z: Gamma rays
The diagram shows an image of an object being reflected off a plane mirror.
Z
Which are examples of resonance? Check all that apply.
a note being played on a saxophone an opera singer breaking a glass with her voice a person pushing a swing at the rate it naturally oscillates back and forth
Which will produce a magnetic field?
a wire carrying a current
Two waves are shown. Each wave has the same frequency and velocity. However, Wave B carries more energy.
amplitude
The graph shows the range of frequencies commonly heard by some animals.
bats moths cats
When two waves are in sync with each other and occupy the same place at the same time, how is the resulting wave determined?
by adding the amplitude of the two waves
Sunlight is shown filtering through clouds.
diffraction, because light is bent around the clouds
A patient is receiving treatments for brain cancer. Which electromagnetic waves are most likely being used as part of the treatment?
gamma ray
What best describes the relationship between wavelength and frequency in an electromagnetic wave?
inversely proportional
If the amplitude of a wave increases by a factor of 4, how is the intensity changed?
it increases by a factor of 16
What best describes the refraction of light rays?
light bending when it passes through a lens
SONAR stands for "sound navigation and ranging," and it is used to map and explore the ocean floor.
longitudinal and mechanical
What best describes a sound wave?
longitudinal and mechanical
A tuning fork is vibrating the air around it. What best describes the waves produced by the tuning fork?
mechanical, because the vibrating tuning fork makes air molecules around it vibrate
An ambulance emits a frequency of 450 Hz from its siren. What frequency is heard by a man as the ambulance moves toward him?
more than 450 Hz
Tonya is modeling the discovery of electromagnetic induction. Which procedure should she use?
moving a magnet into a coil of wire in a closed circuit
What two factors will most likely change the speed of a mechanical wave?
period and wavelength
Which best describes pitch?
the number of cycles per second perceived by the human ear
What two factors affect the speed of a sound wave as it travels through a medium?
the type of medium and the temperature of the medium
A pebble is dropped in a pond.
transverse, because the water molecules move up and down, which is perpendicular to the motion of the wave
A lab technician needs to clean medical instruments that have been exposed to bacteria. Which electromagnetic wave would be most useful for this task?
ultraviolet
Two pulses are moving along a string. One pulse is moving to the right and the second is moving to the left. Both pulses reach point X at the same instant.
up, flat, down
Julia produces a 2 mA current by moving the south pole of a bar magnet into a solenoid. The solenoid contains 150 loops of wire.
using more loops of wire in the coil
Which changes will cause an increase in the magnetic field of a solenoid? Check all that apply.
using more wire loops using a larger current decreasing the spacing between loops
Which change would reverse the direction of the electric current generated through electromagnetic induction?
using the opposite pole of the magnet
Which equations represent the relationship between wavelength and frequency for a sound wave? Check all that apply.
v = hf h = v/f f = v/h (the "h" represents the lambda...just go with it)
The diagram represents wavelengths of different colors of visible light that pass by in a specific time period.
violet
Consider the ranges of pitches made by these instruments and vocals.
violin, clarinet, French horn, tuba
Which lists the waves in order of frequency, from highest to lowest?
visible light, infrared, microwaves
The data table shows the sound levels of common noise sources.
woodworker
A band director instructs students to play a pitch louder. How will the sound wave change when the band plays the same pitch louder?
The amplitude of the sound wave will increase.
Joan makes the device shown in her science class.
The field would reverse its poles.
What best describes white light as it travels through a prism? Check all that apply.
The light slows down. The light bends in the prism. Light reflects off of the surface of the prism. The white light breaks into its component colors.
What is the purpose of a rearview mirror in a car?
The mirror allows the light to be reflected so the objects behind the car can be seen.
Juan is standing on the street. An ambulance moves toward him and then passes by.
The pitch drops to a lower pitch once the ambulance passes by Juan.
A 4.0 cm object is 6.0 cm from a convex mirror that has a focal length of 8.0 cm. What is the distance of the image from the mirror?
-24 cm
A boy yells in a narrow valley. The sound reflects off of a boulder that is 80 m away. How long will it take to hear the echo if the speed of a sound wave is 320 m/s?
0.50 seconds
A sound wave with a power of 8.8 × 10-4 W leaves a speaker and passes through section A, which has an area of 5.0 m2.
1.8 × 10-4 W/m2
