Question

A stationary source emits sound wave of frequency $500Hz$. Two observers moving along a line passing through the source detect sound to be of frequencies $480Hz$ and $530Hz$, Their respective speeds are, in $m{s}^{-1}$
(Given speed of sound$=300ms)$

• A. $16,14$
• B. $12,18$
• C. $12,16$
• D. $8,18$

Answer 1

Answer: (B)

$12,18$

$f=480=\frac{300-v_1}{300}\times 500$
$\frac{1440}{5}=300-v_1$
$v_1=\frac{60}{5}=12m/s$
$530=\frac{300+v_2}{300}\times 500$
$1590=1500+5v_2$
$5v_2=90$
$v_2=18m/s$