Question

The driver of a car travelling with speed $30\, m/sec$ towards a hill sounds a horn of frequency $600\, Hz.$ If the velocity of sound in air is $330\, m/s,$ the frequency of reflected sound as heard by driver is

• A. 555.5 Hz
• B. 720 Hz
• C. 500 Hz
• D. 550 Hz

Answer 1

Answer: (B)

720 Hz

Answer 2

$n '=v\left(\frac{ c + u }{ c - u }\right)$
$=600\left(\frac{330+30}{330-30}\right)=720\, Hz$