Question

The driver of a car traveling 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. 500 Hz
• B. 550 Hz
• C. 555.5 Hz
• D. 720 Hz

Answer 1

Answer: (D)

720 Hz

$n^{\prime }=v\left[\frac{c+u}{c-u}\right]$

$=600\left[\frac{330+30}{330-30}\right]=720Hz$