Question

When a sound is going away from a stationary observer with the velocity equal to that of sound in air, then the frequency heard by observer is n times the original frequency. The value of n is

• A. 0.5
• B. 0.25
• C. 1
• D. no sound is heard

Answer 1

The correct option is A 0.5

According to the Doppler effect in sound,
${\nu }^{\prime }=\frac{V_{sound}}{V_{sound}+V_{source}}\times \nu$
here,
$V_{sound}=V_{source}$
therefore,
${\nu }^{\prime }=\frac{V_{sound}}{V_{sound}+V_{source}}\times \nu =\frac{1}{2}\times \nu$.
Option A is correct.