Question

The apparent frequency of sound heard by a listner is 10% more than the actual frequency of the note emitted by the source when the source moves towards the stationary listner with velocity v. When the source moves with a velocity 2v, the apparent frequency will be more than the actual frequency by

• A. 17.5%
• B. 20%
• C. 22.2%
• D. 24.5%

Answer 1

Answer: (C)

22.2%

The apparent frequency of sound from a moving source (with velocity $V_s$) heard by a stationary listener is:

$n_1=n\frac{V}{V-V_s}$.

In first case: $n_1/n=11/10$

Using this in first equation we will get: $V_s/V=1/11$.

Now in the second case the $V_s$ become double.

So the apparent frequency will be: $n_2=n\frac{V}{V-2V_s}$.

Using $V_s/V=1/11$ we can get that the apparent frequency will be more than the actual frequency by $22.2$%.