Question

A source of sound moves towards a stationary observer with a speed one

third that of sound. If the frequency of the sound from the source is 100
Hz, the apparent frequency of the sound heard by the observer is
A. 67 Hz
B. 100 Hz
D. 75 Hz
C. 150 Hz

Answer 1

A. 67 Hz

Step-by-step explanation:

The apparent frequency of the sound heard by the observer can be calculated using the Doppler effect equation:

f_app = f_src (1 - v/c)

where f_app is the apparent frequency of the sound, f_src is the frequency of the sound, v is the velocity of the source, and c is the speed of sound.

Substituting the given values, we get:

100 = 100((1/3)/(343))

Solving for f_app, we get:

f_app = 100((2/3)/(3/3)) = 100/2 = 50 Hz

Therefore, the correct answer is A.