Question

A whistle giving out $450Hz$, approaches a stationary observer at a speed of $33m/s$. The frequency heard by the observer in $Hz$ is (speed sound = $330m/s$)

• A. $4409$
• B. $429$
• C. $517$
• D. $500$

Answer 1

Answer: (D)

$500$

source is moving towards the observer
$f^{\prime }=f\left(\frac{V}{V-V_S}\right)$
$=450\left(\frac{330}{330-33}\right)$
$=450\left(\frac{330}{297}\right)$
$f^{\prime }=500Hz$