Question

A person moves towards a stationary source of sound, with a velocity of one – fifth of the velocity of sound. The apparent frequency of the sound as heard by a person

• A. Increases by 10 %
• B. increases by 20 %
• C. decreases by 10 %
• D. decreases by 20 %.

Answer 1

The correct option is B

increases by 20 %

$n‘=n\left(\frac{V-V_o}{V-V_S}\right)$

$=n\frac{n(V+V_o)}{V}=\frac{6}{5}n=1.2n=20$~increase