Question

A stationary source of sound is emitting sound of frequency $500Hz$. Two observers A and B lying on the same line as the source, observe frequencies $480Hz$ and $530Hz$ respectively. The velocity of A and B respectively are (in m/s), speed of sound = $300m/s$.

• A. $12,18$
• B. $8,18$
• C. $18,8$
• D. $18,12$

Answer 1

The correct option is A $12,18$

$f_A=\left(\frac{300-V_A}{300}\right)\times 500=480$
$\Rightarrow 15000-50V_A=14400$
$\Rightarrow \frac{600}{50}=V_A\Rightarrow V_A=12m/s$
$f_B=\left(\frac{300+V_B}{300}\right)\times 500=530$
$\Rightarrow V_B+300=318$
$V_B=18m/s$