Question

A stationary sound source S of frequency 334 Hz and a stationary observer O are placed near reflecting surface moving away from the source with velocity 2m/s as shown in figure. Velocity of sound waves in air $v=330$ m/s. The apparent frequency of echo is -

• A. $332Hz$
• B. $326Hz$
• C. $334Hz$
• D. $330Hz$

Answer 1

Answer: (D)

$F_{\text{echo }}=f_{ac}\left[\frac{V-V_0}{V+V_s}\right]$
$=334\left[\frac{330-2}{330+2}\right]$
$=334\times \frac{328}{332}=330Hz$