A 520-Hz whistle is moved toward a listener at a speed of 50 m/s.At the same time,the listener moves at a speed of 70 m/s in a direction away from the whistle.What is the apparent frequency heard by the listener? (The speed of sound is 340 m/s. )

Question

Quizplus · Accepted Answer

The formula for Doppler effect when the source is moving and the observer is stationary is:

f' = f * (v + v₀) / (v + vᵢ)

where:
f' is the apparent frequency heard by the listener
f is the actual frequency of the whistle
v is the speed of sound
v₀ is the speed of the source (in this case the whistle)
vᵢ is the speed of the observer (in this case the listener)

Plugging in the given values:

f' = 520 * (340 + 50) / (340 - 70)
f' = 484 Hz

Therefore, the apparent frequency heard by the listener is 484 Hz, which corresponds to choice B.

A 520-Hz Whistle Is Moved Toward a Listener at a Speed