The Doppler Effect
15.7 The Doppler Effect
By the end of this section, you will be able to:
- Explain the change in observed frequency as a moving source of sound approaches or departs from a stationary observer
- Explain the change in observed frequency as an observer moves toward or away from a stationary source of sound
Consider detectors of water waves at three locations A, B, and C in the figure. Which of the following statements is true?
|(a) The wave speed is highest at location A.|
|(b) The wave speed is highest at location C.|
|(c) The detected wavelength is largest at location B.|
|(d) The detected wavelength is largest at location C.|
|(e) The detected frequency is highest at location C.|
|(f) The detected frequency is highest at location A.|
|If a 1.00-kHz sound source moves at a speed of 50.5 m/s toward a listener who moves at a speed of 25.0 m/s in a direction away from the source, what is the apparent frequency heard by the listener? (Use 343 m/s as the speed of sound in air.)|
|(a) 808 Hz|
|(b) 935 Hz|
|(c) 1000 Hz|
|(d) 1087 Hz|
|(e) 1258 Hz|
The frequency of the train whistle when the train is not moving is 495 Hz. What sound frequency does each person hear?
A bat flying 9.00 m/s emits a 65.0 kHz sound wave. It reflects off a moth fleeing at 2.00 m/s in the same direction the bat is flying. What frequency does the bat hear when the sound returns?
You are at an outdoor concert with a wind blowing at 10 m/s from the performers toward you. Is the sound you hear Doppler-shifted? If so, is it shifted to lower or higher frequencies?