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Waves and Sound: Properties and Behavior, Exams of Quantum Physics

Various aspects of waves and sound, including their types (longitudinal and transverse), behavior when interacting with different media, and the effects of temperature and frequency on their propagation. Topics covered include wave propagation, seismic waves, refraction, reflection, and echolocation.

Typology: Exams

2012/2013

Uploaded on 03/29/2013

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PHYS 1400 Sample Exams: Waves and Sound
1. An oscillation, or vibration
A) is a completely random motion. For example, when a fly buzzes around you, the path of his
motion is an oscillation.
B) is not completely random, because the motion cannot repeat. For example, if the fly circles
around your head once, he can keep flying, but never follow that same path again.
C) is not random at all. If you are going to use that fly as an example, then you have to look at its
wings. The wings move up and down, over and over (and really fast), but they stay attached to the
fly. The wings are oscillating.
D) is a back-and-forth motion that repeats, but not like the fly's wings; it has to be a back-and-forth
motion, it cannot be an up-and-down motion.
2. A wave is
A) an oscillation in time only. C) an oscillation in time propagated through space.
B) an oscillation in space only. D) a vibration, not an oscillation!
3. As a wave propagates,
A) the medium is pulled along with the traveling wave.
B) the medium actually travels in the opposite direction, as the wave "pushes off" the molecules.
C) the molecules of the medium vibrate, but do not propagate forward with the wave.
D) the medium remains rigid, neither vibrating nor propagating as the wave passes.
4. Compare a longitudinal and a transverse wave.
A) Longitudinal waves vibrate parallel to the direction of propagation, transverse perpendicular.
B) Backwards! Longitudinal vibrate perpendicular to the direction of propagation, and transverse
waves vibrate parallel to the direction of propagation.
C) Longitudinal waves have longer wavelength and transverse waves have greater amplitude.
D) Backwards! Transverse have longer wavelength, longitudinal have greater amplitude.
5. Compare sound and light waves.
A) Sound waves are transverse, and so are light waves.
B) Sound waves are longitudinal, and so are light waves.
C) Sound waves are transverse, light waves are longitudinal.
D) Sound waves are longitudinal, light waves are transverse.
6. Sound waves
A) are exclusively longitudinal. C) are neither longitudinal nor transverse.
B) are exclusively transverse. D) have longitudinal and transverse components.
7. Light waves
A) are exclusively longitudinal. C) are neither longitudinal nor transverse.
B) are exclusively transverse. D) have longitudinal and transverse components.
8. Seismic waves
A) are exclusively longitudinal. C) are neither longitudinal nor transverse.
B) are exclusively transverse. D) have longitudinal and transverse components.
9. A seismograph is used to record earthquake tremors. The same earthquake can be recorded on
different seismographs located in different places. This data can then be used to locate the epicenter
of the earthquake. Geologists have labeled seismic waves as S-waves or P-waves.
A) This is arbitrary, and does not mean anything significant. American geologists call them S-waves
(S for seismic), and German geologists call them P-waves (P for planierungsraupenfahrzeug).
B) S- and P-waves are two different types of seismic waves. The S-waves are transverse, and the P-
waves are longitudinal.
C) Backwards! The S-waves are longitudinal, and the P-waves are transverse.
D) The S-waves are seismic waves that have been recorded on a seismograph. P-waves are seismic
waves that have been predicted, but not recorded or measured in any way.
10. Pushing and pulling an accordion parallel to its axis, making the bellows expand and contract
A) causes a transverse wave. C) causes an obfuscation wave.
B) causes a longitudinal wave. D) does not result in wave motion of any kind.
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PHYS 1400 Sample Exams: Waves and Sound

  1. An oscillation, or vibration A) is a completely random motion. For example, when a fly buzzes around you, the path of his motion is an oscillation. B) is not completely random, because the motion cannot repeat. For example, if the fly circles around your head once, he can keep flying, but never follow that same path again. C) is not random at all. If you are going to use that fly as an example, then you have to look at its wings. The wings move up and down, over and over (and really fast), but they stay attached to the fly. The wings are oscillating. D) is a back-and-forth motion that repeats, but not like the fly's wings; it has to be a back-and-forth motion, it cannot be an up-and-down motion.
  2. A wave is A) an oscillation in time only. C) an oscillation in time propagated through space. B) an oscillation in space only. D) a vibration, not an oscillation!
  3. As a wave propagates, A) the medium is pulled along with the traveling wave. B) the medium actually travels in the opposite direction, as the wave "pushes off" the molecules. C) the molecules of the medium vibrate, but do not propagate forward with the wave. D) the medium remains rigid, neither vibrating nor propagating as the wave passes.
  4. Compare a longitudinal and a transverse wave. A) Longitudinal waves vibrate parallel to the direction of propagation, transverse perpendicular. B) Backwards! Longitudinal vibrate perpendicular to the direction of propagation, and transverse waves vibrate parallel to the direction of propagation. C) Longitudinal waves have longer wavelength and transverse waves have greater amplitude. D) Backwards! Transverse have longer wavelength, longitudinal have greater amplitude.
  5. Compare sound and light waves. A) Sound waves are transverse, and so are light waves. B) Sound waves are longitudinal, and so are light waves. C) Sound waves are transverse, light waves are longitudinal. D) Sound waves are longitudinal, light waves are transverse.
  6. Sound waves A) are exclusively longitudinal. C) are neither longitudinal nor transverse. B) are exclusively transverse. D) have longitudinal and transverse components.
  7. Light waves A) are exclusively longitudinal. C) are neither longitudinal nor transverse. B) are exclusively transverse. D) have longitudinal and transverse components.
  8. Seismic waves A) are exclusively longitudinal. C) are neither longitudinal nor transverse. B) are exclusively transverse. D) have longitudinal and transverse components.
  9. A seismograph is used to record earthquake tremors. The same earthquake can be recorded on different seismographs located in different places. This data can then be used to locate the epicenter of the earthquake. Geologists have labeled seismic waves as S-waves or P-waves. A) This is arbitrary, and does not mean anything significant. American geologists call them S-waves (S for seismic), and German geologists call them P-waves (P for planierungsraupenfahrzeug). B) S- and P-waves are two different types of seismic waves. The S-waves are transverse, and the P- waves are longitudinal. C) Backwards! The S-waves are longitudinal, and the P-waves are transverse. D) The S-waves are seismic waves that have been recorded on a seismograph. P-waves are seismic waves that have been predicted, but not recorded or measured in any way.
  10. Pushing and pulling an accordion parallel to its axis, making the bellows expand and contract A) causes a transverse wave. C) causes an obfuscation wave. B) causes a longitudinal wave. D) does not result in wave motion of any kind.
  1. A transverse wave A) occurs when the direction of oscillation is perpendicular to the direction of travel. B) occurs when the direction of oscillation is parallel to the direction of travel. C) is identical in every way to a longitudinal wave.
  2. The rarefactions of a longitudinal wave A) are analogous to the troughs of a transverse wave. B) are analogous to the amplitude of a transverse wave. C) are equal to the wavelength times the frequency of the wave. D) occur where the molecules of the vibrating medium are closest together.
  3. The compressions of a longitudinal wave A) are analogous to the crests of a transverse wave. B) are analogous to the amplitude of a transverse wave. C) are equal to the wavelength times the frequency of the wave. D) occur where the molecules of the vibrating medium are farthest apart.
  4. The troughs of a transverse wave A) are analogous to the compressions of a longitudinal wave. B) are analogous to the rarefactions of a longitudinal wave. C) are analogous to the nodes of a longitudinal wave. D) occur where the molecules of the vibrating medium are closest together.
  5. An alarm clock vibrates with a frequency of 68 Hz. The speed of the resulting sound wave through the air is 340 m/s. What is its wavelength? A) 1 m B) 2 m C) 3 m D) 4 m E) 5 m
  6. Gusts of wind make the Sears Tower sway back and forth, completing a cycle every 10 seconds. A) Its frequency = 1/10 Hz, and its period is 10 seconds. B) Its frequency = 10 Hz, and its period is 1/10 seconds. C) Its frequency = 1 Hz, and its period is 1 second. D) Its frequency = 10 Hz, and its period = 10 seconds.
  7. Two sound waves travel through dry air at 20°C. The second wave has twice the frequency of the first. A) Its wavelength is twice the wavelength of the original wave. B) Its wavelength is half the wavelength of the original wave. C) Its speed is twice the speed of the original wave. D) Its speed is half the speed of the original wave.
  8. If the temperature of the air increased suddenly to 30°C, A) the wave speed would increase as well. B) the wave speed would decrease, not increase. C) the speed would remain the same, but the frequency would increase. D) both the frequency and the wavelength would increase at the same rate as the temperature.
  9. How is refraction different from reflection? A) Reflection occurs when a wave strikes a boundary that it cannot cross, so it bounces. Refraction occurs when the wave strikes a boundary, but can continue to travel through the new medium. B) When a wave is reflected, it bounces straight back in the direction from which it came. When a wave is refracted, it bounces off the boundary in some random direction. C) A reflected wave strikes a boundary and keeps going, but it slows down. A refracted wave strikes the same boundary and keeps going, but it speeds up. D) A reflected wave always bends from warm air toward cold air. A refracted wave always bends from cold air toward warm air.
  1. For a sound to be audible, it must have A) frequency between 20Hz and 20,000Hz. It must also have an intensity greater than 10-12^ W/m^2. B) frequency between 20Hz and 20,000Hz. But the intensity must be greater than 1W/m^2. C) any frequency at all, as long as the intensity is greater than 1W/m^2. D) any frequency at all, as long as the intensity is less than 10-12^ W/m^2. E) any frequency, any intensity. Whenever molecules vibrate, human ears hear them.
  2. An infrasonic pulse has a frequency A) less than 20Hz C) between 20 Hz and 20,000Hz. B) greater than 20 Hz. D) greater than 20,000Hz.
  3. An ultrasonic pulse A) has an intensity greater than the threshold of pain. B) has an intensity less than the threshold of hearing. C) has a frequency in the audible range of the human ear. D) has a frequency too low to be heard by the human ear. E) has a frequency too high to be heard by the human ear.
  4. When bats use echolocation to hunt for food, they emit A) a stream of radioactive particles that instantly kills anything it hits. B) a beam of light, because they hunt at night. How else can they see their food? C) an infrasonic pulse. They use a very low frequency so as not to scare the insects. D) an audible pulse. This is why people are afraid of bats, because they sound so scary. E) an ultrasonic pulse. The frequency is too high for human ears to hear.
  5. In space, no one can hear you scream. A) True; your small voice would be drowned out by the heavenly music of the spheres. B) False; sound travels especially well through vacuum, so your voice carries over infinite distances. C) True; sound cannot travel through space because there is no medium to propagate the wave. D) False; this may be a catchy tag line for a Hollywood movie, but it has nothing whatsoever to do with physics!
  6. In defense of the Intergalactic Zambonian Empire, your starship, Ice Princess, fires a photon torpedo at an invading destroyer. As the enemy ship explodes into millions of pieces, you hear A) a roaring, rushing sound; very loud and exciting! Long live the Zambonian Empire! B) absolutely nothing other than the noise within your own ship.
  7. Sound travels best through a medium that is A) extremely dense, like lead. C) extremely cold, like snow. B) amorphous and lightweight, like styrofoam. D) highly elastic, like steel.
  8. The speed of sound in water A) is greater than the speed of sound through air. B) is zero because water does not transmit sound. C) is greater than the speed of sound through steel.
  9. The speed of sound in steel A) is greater than the speed of sound through air. B) is zero because steel does not transmit sound. C) is less than the speed of sound through water.
  10. Why does styrofoam or cork make a good sound insulator? A) The crystalline structure makes it hard to propagate sound energy from molecule to molecule. B) Amorphous structure and many air pockets make it very difficult to pass the sound energy along. C) Styrofoam is white, and cork is typically light beige. Lighter colors reflect sound, not transmit it. D) These are dense materials, and density means there are more molecules per volume, so the sound energy has to undergo many more transmissions from molecule to molecule, which takes a lot of time.
  1. Why does sound travel faster in warm air than cold? A) It doesn't. Cold air is denser, so sound travels faster in cold air. B) Warm air is denser, so sound travels faster. C) Warm air molecules move faster than cold air molecules, so sound travels faster. D) The speed of sound in air does not depend on temperature at all.
  2. Sound waves traveling through air of uneven temperatures A) are bent from warm air toward cool air. B) are bent from cool air toward warm air. C) continue to travel in a straight line. D) resonate between cold and warm air until they cancel out.
  3. The superposition principle is based on the idea that A) two particles cannot occupy the same space at the same time. B) two particles can occupy the same space at the same time: they superimpose to result in a new particle having the combined mass: m = m 1 + m 2. C) two waves can occupy the same space at the same time: they superimpose to result in a new wave having the combined amplitude: A = A 1 + A 2. D) two waves cannot occupy the same space at the same time. If they try to, the result is a nuclear explosion, because the energy of one wave is "fighting" the energy of the other wave. E) two waves cannot occupy the same space at the same time. Neither can two particles. Which must mean that there really isn't any superposition of matter or energy. What a crazy universe this is!
  4. Two transverse waves have the same amplitude, frequency, and wavelength. If they are in phase, A) the resulting superposition will be a wave with twice the amplitude. B) the resulting superposition will be a wave with twice the wavelength. C) the resulting superposition will be a wave with twice the frequency. D) the resulting wave won't be a wave at all; they cancel completely.
  5. Two transverse waves have the same amplitude, frequency, and wavelength. If they are out of phase, A) they will interfere constructively, and reinforce each other. B) they will interfere destructively and cancel each other. C) they will interfere instructively and teach each other physics. D) they will interfere perspectively and disappear on the horizon.
  6. Constructive interference occurs when two waves are A) in phase: crest 1 matches crest 2 , and the resulting wave has an amplitude A = A 1 + A 2. B) out of phase: crest 1 matches trough 2 , and the waves cancel. Amplitude A = 0. C) partially in phase, partially out of phase: the crests and troughs are not perfectly aligned, which constructs a new wave that looks nothing like either of the original waves. D) traveling in away from each other in two different directions. The energy is then transmitted to a greater area than if they were traveling in the same direction, so it can be used for something constructive.
  7. What happens when two waves meet that are not perfectly in phase or perfectly out of phase? A) Nothing. The two waves will not interfere at all. B) The waves will still interfere constructively. C) The waves will interfere, but they must cancel completely. D) The waves do not cancel completely or reinforce; you must use the superposition principle to determine the amplitude of the new wave at each point. The new wave may have an odd shape.
  8. A standing wave will be formed when a guitar string is plucked. A) The string is fixed at both ends: this means that each end must be a node. B) The standing wave will have an anti-node (maximum amplitude) at each end of the string. C) The string is only fixed at one end. To make a standing wave, there must be one fixed and one free end. D) Both ends of the string are free, which is why answer B was right to begin with! A standing wave can only form when both ends of the string are free. Neither end can be fixed. E) None of these answers is correct, because you cannot form a standing wave using a guitar string. Steel strings cannot propagate waves of any kind.