23 Traveling Waves: Review and Homework

Important Terms

• speed
• medium
• propagate
• transverse (wave)
• longitudinal (wave)
• wave
• wavelength
• crest
• trough
• pulse
• amplitude
• compression
• rarefaction

Review Questions

1. How does a wave move? How is the motion of a wave different than the motion of the material in which the wave travels?
2. What is a pulse? What is a wave? How are the two terms related?
3. How does sound move? Does it speed up or slow down as it travels?
4. Explain what happens to the speed and amplitude of a sound wave as the sound dies out.
5. What factors affect the speed of sound? What factors don’t?
6. Some people think high pitched sounds travel faster than low pitched ones. Is this true? Discuss how at least one experience from real life supports (or disproves) this idea.
7. Describe the motion of the air particles in a sound wave. Compare the motion of the air particles to the motion of the sound itself.
8. Explain the difference between longitudinal and transverse waves.
9. Draw two L-waves with the same amplitude but different wavelength. Draw two L-waves with different wavelength but the same amplitude.
10. Draw a T-wave and label the amplitude and the wavelength on your diagram.
11. Explain the relationship among wave speed, frequency and wavelength.
12. Explain why high frequency sources produce short wavelength sounds.

Numericals

1. The width of Shayna’s bedroom is 25 feet. How long does it take sound to travel across her bedroom? How long does it light to travel across her bedroom?
2. The lowest sounds pitched most people can hear are in the range of 20 to 50 Hz. Approximately how long are the wavelengths of such sounds? Give an example of a real world distance this wavelength corresponds to (e.g. the width of your finger, diameter of a coin, the length of your arm, length of a city bus, etc.)
3. The highest sounds most people can hear are in the range of 10 to 20 kHz. Approximately how long are the wavelengths of such sounds? Give an example of a real world distance this wavelength corresponds to (e.g. the width of your finger, diameter of a coin, the length of your arm, length of a city bus, etc.)
4. Some whales can locate objects near them by sending out a brief pulse of sound and listening for the echo. If the delay between when the whale makes a noise and hears the echo is 120 milliseconds, how far away from the whale is the object?
5. Most bats can locate objects near them by sending out a brief pulse of sound and listening for the echo. If the delay between when the bat makes a noise and hears the echo is 120 milliseconds, how far away from the bat is the object?
6. A hammer taps on the end of a 4.00 meter long metal bar. A microphone at the other end of the bar picks up two pulses of sound, one that travels through the metal and one that travels through the air. The pulses arrive 9.00 milliseconds apart. What is the speed of sound in this metal?
7. Sonar is a device that uses reflected sound waves to measure underwater depths. If a sonar signal has a frequency of 288 Hz, what is the wavelength of the sonar signal?
8. A ship anchored at sea is rocked by waves that have crests 14 m apart. The waves travel at 7.0 m/s. How often do the wave crests reach the ship?