Waves Preview Understanding Concepts Reading Skills Interpreting Graphics

Understanding Concepts 1. 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

Understanding Concepts 1. 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

Understanding Concepts, continued 2. 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? F. The resulting wave has zero amplitude. G. The resulting wave has twice the amplitude of the original waves. H. The resulting wave has zero wavelength. I. The resulting wave has a wavelength twice as long as the original waves.

Understanding Concepts, continued 2. 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? F. The resulting wave has zero amplitude. G. The resulting wave has twice the amplitude of the original waves. H. The resulting wave has zero wavelength. I. The resulting wave has a wavelength twice as long as the original waves.

Understanding Concepts, continued 3. 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. 2.5 cm B. 6 cm C. 15 cm D. 18 cm

Understanding Concepts, continued 3. 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. 2.5 cm B. 6 cm C. 15 cm D. 18 cm

Understanding Concepts, continued 4. Many home computers have a frequency of over 1 GHz, meaning 1 × 109 cycles per second. What is the period of a 1 GHz computer?

Understanding Concepts, continued Many home computers have a frequency of over 1 GHz, meaning 1 × 109 cycles per second. What is the period of a 1 GHz computer? Answer: 1 × 10-9 seconds per cycle

Understanding Concepts, continued 5. 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 Concepts, continued 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? Answer: The pitch the motorcyclist hears is higher.

Understanding Concepts, continued 6. Why do waves tend to travel faster through a solid medium than through a liquid or a gas?

Understanding Concepts, continued Why do waves tend to travel faster through a solid medium than through a liquid or a gas? Answer: The particles are closer together and more tightly bound to each other.

THE DOPPLER EFFECT IN SPACE Reading Skills 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.

Reading Skills, continued THE DOPPLER EFFECT IN SPACE, continued 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 is also responsible for the red shifts of distant galaxies. These shifts indicate that distant galaxies are moving away from us and from each other.

Reading Skills, continued 7. If light from a celestial object is observed to shift towards the blue end of the spectrum, what conclusion can be drawn? F. The object is moving towards Earth. G. The object is reflecting radio waves emanating from the Earth. H. The velocity of the object is increasing. I. The velocity of the light emanating fro the object is decreasing.

Reading Skills, continued 7. If light from a celestial object is observed to shift towards the blue end of the spectrum, what conclusion can be drawn? F. The object is moving towards Earth. G. The object is reflecting radio waves emanating from the Earth. H. The velocity of the object is increasing. I. The velocity of the light emanating fro the object is decreasing.

Reading Skills, continued 8. 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 train experience the Doppler effect? Why or why not?

Reading Skills, continued 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 train experience the Doppler effect? Why or why not? Answer: No; because the trains aren’t moving in relation to each other.

Interpreting Graphics 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.

Interpreting Graphics, continued 9. In Graph A, “Wave 1” is the resultant wave. What type of interference is shown in Graph A? A. constructive C. complete destructive B. partial destructive D. constructive and destructive

Interpreting Graphics, continued 9. In Graph A, “Wave 1” is the resultant wave. What type of interference is shown in Graph A? A. constructive C. complete destructive B. partial destructive D. constructive and destructive

Interpreting Graphics, continued 10. In Graph B, which wave is the resultant wave? F. Wave 4 H. Wave 6 G. Wave 5 I. This cannot be determined.

Interpreting Graphics, continued 10. In Graph B, which wave is the resultant wave? F. Wave 4 H. Wave 6 G. Wave 5 I. This cannot be determined.

Interpreting Graphics, continued 11. What characteristic do all six of these waves have in common?

Interpreting Graphics, continued 11. What characteristic do all six of these waves have in common? Answer: They all have the same wavelength.

Interpreting Graphics, continued The following graph describes two waves. Use this graph to answer questions 12 and 13.

Interpreting Graphics, continued 12. If these waves interfere with each other, what will result? A. constructive interference B. destructive interference C. constructive interference in some places and destructive interference in others D. neither constructive nor destructive interference

Interpreting Graphics, continued 12. If these waves interfere with each other, what will result? A. constructive interference B. destructive interference C. constructive interference in some places and destructive interference in others D. neither constructive nor destructive interference

Interpreting Graphics, continued 13. The two waves above have identical amplitudes. What else would they have in common if the x-axis is in units of time? What else would they have in common if the x-axis is in units of distance?

Interpreting Graphics, continued 13. The two waves above have identical amplitudes. What else would they have in common if the x-axis is in units of time? What else would they have in common if the x-axis is in units of distance? Answer: Time: frequency and period. Distance: wavelength.