AP Physics 1 Question 460: Answer and Explanation
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8. A speaker is emitting a sound wave with a wavelength λ. If a person is standing in an adjacent room, which of the following would NOT affect the perceived wavelength of the wave?
- A. The person starts running further away from the speaker.
- B. The air pressure in the person's room is increased.
- C. The temperature in the person's room is increased.
- D. The person's room is filled with water.
Correct Answer: B
Choice (A) would be an example of the Doppler effect. Choices (C) and (D) would both affect the speed of the wave, which would change the wavelength because v = fλ; the frequency of the wave would not change, meaning that the wavelength would change proportionally to the speed. Choice (B) is correct because pressure has no effect on the speed of sound. If the speed and frequency both remain constant, then the wavelength must as well.