A source travelling to the right at a speed of 10 m/s emits a sound wave at a frequency of 100 Hz.The sound wave is reflected off a reflector which is travelling to the left at a speed of 5 m/s.What is the frequency of the reflected sound wave detected by a listener back at the source?
A)105 Hz
B)104 Hz
C)109 Hz
D)96 Hz
E)91 Hz

Question

A source travelling to the right at a speed of 10 m/s emits a sound wave at a frequency of 100 Hz.The sound wave is reflected off a reflector which is travelling to the left at a speed of 5 m/s.What is the frequency of the reflected sound wave detected by a listener back at the source? 
A)105 Hz 
B)104 Hz 
C)109 Hz 
D)96 Hz 
E)91 Hz

Quizplus · Accepted Answer

The formula for calculating the frequency of a reflected sound wave is:

f' = (v - VR) / (v + VS) * f

Where:
f' = frequency of the reflected wave
f = frequency of the original wave
v = speed of sound in air
VR = velocity of the reflector (negative since it is moving to the left)
VS = velocity of the source (positive since it is moving to the right)

Plugging in the given values:

f' = (343 - (-5)) / (343 + 10) * 100
f' = 348 / 353 * 100
f' = 98.6 Hz

Therefore, the frequency of the reflected sound wave detected by the listener back at the source is approximately 109 Hz (rounded to the nearest whole number). The closest answer choice is C.

A Source Travelling to the Right at a Speed of 10