; Chapter 15 Waves Review
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# Chapter 15 Waves Review

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```									                        Chapter 15 Waves: Review
USING KEY TERMS

1. How would you describe the amplitude of a wave using the words crest, line of origin and
trough?

2. Explain the difference between waves bending due to refraction and diffraction.

3. Draw a picture of a standing wave, and label a node and an anti-node.

4. How do beats help determine whether two sound waves are of the same frequency? Use the

EXPLAINING KEY IDEAS

5. Imagine you are shaking the end of a rope to create a series of waves. What will you observe
happen to the wavelength and the frequency if you begin shaking the rope more quickly?

6. Describe the changes in elastic potential energy and kinetic energy that occur when a rubber
ball is dropped from a height of 10 ft above a basketball court and bounces several times
before coming to rest.

7. Use the kinetic theory to explain the difference in the speed of sound in solids, liquids, and
gases.

CRITICAL THINKING

8. When you are watching a baseball game, you may hear the crack of the bat a short time after
you see the batter hit the ball. Why does this happen? (Hint: Consider the relationship between
the speed of sound and the speed of light.)
9. You are standing on a street corner, and you hear a fire truck approaching. As the fire truck
gets closer to you, does the pitch of the siren increase, decrease, or stay constant? Explain your
answer using the Doppler effect as evidence.

10.    If you yell or clap your hands while standing at the edge of a large rock canyon, you may
hear an echo a few seconds later. Explain what type of wave interaction (diffraction,
interference, reflection, or refraction) causes this to happen.

11.   A piano tuner listens to a tuning fork vibrating at 440 Hz to tune a string of a piano. He
hears beats between the tuning fork and the piano string. Is the string in tune? Explain your

12.   A motorcyclist approaches an outdoor concert. How does the pitch that the motorcyclist
hears from the concert differ from the pitch that a stationary listener at the concert hears?

UNDERSTANDING KEY IDEAS

13. A wave is a disturbance that transmits

a. Matter              b. particles        c. energy                d. a medium

14. The speed of a wave depends on the

a. Medium              b. frequency        c. amplitude             d. wavelength

15. Most waves are caused by

a. Velocity            b. amplitude        c. a vibration           d. earthquakes

16. A sound wave is an example of

a. An electromagnetic wave                 c. a longitudinal wave

b. A transverse wave                       d. a surface wave

17. In an ocean wave, the molecules of water
a. move perpendicularly to the direction of wave travel.

b. move parallel to the direction of wave travel.

c. move in ellipses.

d. don’t move at all.

18. Half the vertical distance between the crest and the trough of a wave is called the

a. frequency            b. wavelength          c. crest               d. amplitude

19. The number of waves passing a given point per unit of time is called the

a. frequency            b. wavespeed           c. wavelength          d. amplitude

20. The combining of waves as they meet is known as

a. Crest                b. noise        c. interference        d. the Doppler effect

21. The Greek letter λ is often used to represent a wave’s

a. Period               b. wavelength          c. frequency           d. amplitude

22. A wave pool at a water amusement park has a machine at one end that generates regular
waves that are 7.5 m long. At the other end, waves crest over the side every 5 s. How fast are
the waves traveling?

a. 0.2 m/s              b. 0.67 m/s            c. 1.5 m/s             d. 37.5 m/s

23.Two waves that have exactly the same wavelength, frequency, and amplitude are occupying
the same space. If the second wave follows exactly half a wavelength behind the first, what is
true of the resulting wave?

a. The resulting wave has zero amplitude.

b. The resulting wave has twice the amplitude of the original waves.

c. The resulting wave has zero wavelength.

d. The resulting wave has a wavelength twice as long as the original waves.
24. A sine wave measures 12 cm from the top of the crest to the bottom of the trough, and 30 cm
from the top of one crest to the top of the next. What is the amplitude of the wave?

a. 2.5cm              b. 6.0cm                 c. 15.0 cm         d. 18 cm

THE DOPPLER EFFECT IN SPACE

The Doppler effect is defined as a change in the wavelength (or frequency) of waves, as a result of motion
of either the source or the receiver of the waves. If the source of the waves and the receiver are
approaching each other (because of the motion of either or both), the frequency of the waves will increase
and the wavelength will be shortened. As a result, sounds will become higher pitched and light will appear
bluer. If the sender and receiver are moving apart, sounds will become lower pitched and light will appear
redder.

In astronomy, the Doppler effect is used to measure the velocity and rotation of stars and galaxies. Both
blue shifts and red shifts are observed for various objects, indicating relative motion both toward and
away from Earth. The Doppler effect also explains the red shifts of distant galaxies. These shifts indicate
that distant galaxies are moving away from us and from each other.

25.   If light from a celestial object is observed to shift towards the blue end of the spectrum,
what conclusion can be drawn?

a. The object is moving toward Earth.

b. The object is reflecting radio waves emanating from the Earth.

c. The velocity of the object is increasing.

d. The velocity of the light emanating from the object is decreasing.

26.   If two trains are moving down the same track, in the same direction and at the same speed,
and the train in front blows its whistle, will the passengers in the rear of the second train
experience the Doppler effect? Why or why not?

Math Skills

27. Ocean waves are hitting a beach at a rate of 2.0 Hz. The distance between wave crests is 1.5
m. Calculate the speed of the waves.

28. The frequencies of radio waves range from approximately 3.00 × 10 5 Hz to 3.00 × 107 Hz.
What is the range of wavelengths of these waves? Use 3.00 × 108 m/s as the speed of
electromagnetic waves.
29. The note A above middle C on a piano emits a sound wave with wavelength 0.7750 m. What is
the frequency of the wave? Use 341.0 m/s as the speed of sound in air.

30. Many home computers have a frequency of over 1 GHz, meaning 1 × 10 9 cycles per second.
What is the period of a 1 GHz computer?

Graphing Skills

31.    Draw a sine curve, and label its crest, trough, and amplitude.

Interpreting Graphs

32. Find the following values for this wave if the frequency= 25.0 Hz.:
a. Period

b. Wavelength

c. Amplitude

d. Speed

33. For each image below, draw the wave that results from interference between the two waves.

The following two graphs each describe two waves and the resultant wave that occurs when
the original two waves interfere with each other. Use these graphs to answer questions 9–11.
34. In Graph A, “Wave 1” is the resultant wave. What type of interference is shown in Graph A?

a. Constructive                     c. partial destructive

b. complete destructive             d. constructive & destructive

35. In Graph B, which wave is the resultant wave?

a. Wave 4     b. wave 5       c. wave 6     d. can’t be determined

The following graph describes two waves. Use this graph to answer questions 37 & 38.

36. If these waves interfere with each other, what will result?

a. Constructive interference

b. Destructive interference

c. Constructive at some places, destructive in others

d. neither constructive nor destructive interference
37. The two waves have identical amplitudes. What else would they have in common if the x-axis
were in units of time? (frequency or wavelength?) What else would they have in common if the
x-axis were in units of distance? (frequency or wavelength?)

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