Question

a speaker sliding across a table plays a sound with constant frequency, which is represented by the wavefront diagram below. there are stationary observers at points a, b, c, and d. which observer is the speaker traveling away from? a a b b c c d d

Explanation:

The Doppler effect for sound waves: When a source (speaker) moves, the wavefronts are compressed in the direction it's moving towards and stretched (larger wavelength) in the direction it's moving away from. Looking at the wavefront diagram, the wavefronts are more spread out (larger distance between them) on the side of observer A. This means the speaker is moving away from A because the wavefronts are stretched (longer wavelength) as the source recedes from A. For the other observers (B, C, D), the wavefronts are either more compressed or symmetric in a way that doesn't indicate receding from them.

Answer:

a. A