A stationary source of sound produces wave of wavelength L and speed v. Now the source moves away from the observer. What is the wavelength and speed of sound as measured by the observer?
Correct answer: B. Wavelength increases, speed does not change
- A. Wavelength decreases, speed does not change
- B. Wavelength increases, speed does not change
- C. Wavelength increases, speed increases
- D. Wavelength increases, speed decreases
Explanation
If a source producing waves moves away from the observer at a constant speed, then the observed wavelength will be larger than the original wavelength. The speed of the wave remains unchanged. Hence, option B is correct.
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About Wave Speed
Wave speed is the rate at which a disturbance or wave pattern travels through a medium, given by v = fλ, where f is frequency and λ is wavelength. Questions examine how speed changes between media, the relation among frequency, wavelength and period, and why wave speed is not the same as particle vibration speed.
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