A stationary source emits 320 Hz towards a large wall moving directly towards the source at 20 m/s. The speed of sound is 340 m/s. If the reflected frequency received back at the stationary source is N Hz, find N.
Physics · Wave Motion · doppler effect
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Question

A stationary source emits 320 Hz towards a large wall moving directly towards the source at 20 m/s. The speed of sound is 340 m/s. If the reflected frequency received back at the stationary source is N Hz, find N.

Physics · Wave Motion · doppler effect

G1 Physics · Accepted Answer

For a moving reflector approaching the source, the reflected frequency is fᵣ = f×(v+u)/(v−u). Substitute: fᵣ = 320(340+20)/(340−20) = 320×360/320 = 360 Hz. Hence, N = 360.