Basics of Waves Review
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Questions #1-#14
Questions #15-#26
Questions #27-#38
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15. The number of cycles of a periodic wave occurring per unit time is defined as a wave's ____.
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a. wavelength. |
b. period. |
c. amplitude. |
d. frequency. |
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Answer: D This is a basic definition which you should know and be able to apply. |
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Frequency and Period of a Wave |
16. A periodic and repeating disturbance in a lake creates waves which emanate outward from its source to produce circular wave patterns. If the frequency of the source is 2.00 Hz and the wave speed is 5.00m/s then the distance between adjacent wave crests is ___ meter.
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a. 0.200 |
b. 0.400 |
c. 1.25 |
d. 2.50 |
e. 10.0 |
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Answer: D Let w=wavelength; then v = w*f. In this problem, it is given that v=5.00 m/s and f = 2.00 Hz. Substitution and algebra yields w = v / f = 2.50 m. |
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The Anatomy of a Wave | The Wave Equation |
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17. What is the frequency of a wave that has a speed of 0.4 m/s and a wavelength of 0.020 meter?
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a. 10 hertz. |
b. 20 hertz. |
c. 0.008 hertz. |
d. 0.5 hertz. |
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Answer: B Let w=wavelength; then v = w*f. In this problem, it is given that v=5 m/s and w = .02 m. Substitution and algebra yields f=v/w=20 Hz. |
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The Wave Equation |
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18. Many wave properties are dependent upon other wave properties. Yet, one wave property is independent of all other wave properties. Which one of the following properties of a wave is independent of all the others?
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a. wavelength |
b. frequency |
c. period |
d. velocity |
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Answer: D The speed of a wave is dependent upon the properties of the medium through which it moves, not upon the properties of the wave itself. |
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The Speed of a Wave |
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19. A pendulum makes exactly 40 vibrations in 20.0 s. Its period is ____. (Be cautious of the units.)
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a. 0.500 Hz. |
b. 0.500 s. |
c. 2.00 Hz. |
d. 2.00 s. |
e. 8.00 x 102 Hz. |
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Answer: B The period is the time for one complete cycle. If the pendulum takes 20.0 seconds for exactly 40 vibrational cycles, then it must take 0.500 second for one cycle. |
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Frequency and Period of a Wave |
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20. A period of 0.005 seconds would be equivalent to a frequency of ____ Hz.
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a. 20 |
b. 50 |
c. 200 |
d. 500 |
e. 2000 |
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Answer: C The period and the frequency are related by a reciprocal relationship; that is, f = 1/T. |
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Frequency and Period of a Wave |
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The number of waves generated per second by a source is called the frequency of the source.
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a. True |
b. False |
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Answer: A This is a basic definition which you should know and be able to apply. |
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Frequency and Period of a Wave |
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The SI unit for frequency is hertz.
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a. True |
b. False |
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Answer: A Know this like the back of your hand. |
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Frequency and Period of a Wave |
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Doubling the frequency of a wave source (without altering the medium) doubles the speed of the waves.
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a. True |
b. False |
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Answer: B Don't be fooled. Wave speed may equal frequency*wavelength. Yet doubling the frequency only halves the wavelength; wave speed remains the same. To change the wave speed, the medium would have to be changed. |
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The Wave Equation |
24. If the frequency of a wave is doubled and if the speed remains constant, its wavelength is ____.
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a. quartered. |
b. halved. |
c. unchanged. |
d. doubled. |
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Answer: B Wave speed equals frequency*wavelength. So doubling the frequency must halve the wavelength in order for wave speed to remain the same. |
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The Wave Equation |
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25.
Two different ropes with different mass densities are attached to
each other. A pulse is introduced into one end of the rop and
approaches the boundary as shown at the right. At the boundary, a
portion of the energy is transmitted into the new medium and a
portion is reflected. Which one of the diagrams below depicts the
possible location and orientation of the pulse shortly after the
incident pulse reaches the boundary?
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Answer: C The speeds in the two media can be deduced by the distance of the pulses from the boundary. In A and E, the speed is shown as fastest on the right, which makes the transmitted medium the less dense. Rule out A and E since a reflected pulse should not invert when moving from more dense to less dens. Rule out B for just the opposite reasons; the wave is moving from less to more dense and should invert upon reflection. Rule out D because the transmitted pulse never inverts. That leaves C as the answer. |
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Boundary Behavior |
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26. When a pulse reaches a boundary between two different media, it will be____.
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a. reflected, only. |
b. transmitted, only. |
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c. partly reflected and partly transmitted. |
d. neither reflected nor transmitted. |
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Answer: C This is basic information about the boundary behavior of waves. |
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Boundary Behavior |
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