Question

A bus is moving with a velocity of 5 m is towards a wall. The driver blows the horn of frequency 165 Hz. If the speed of sound in air is 335 m is, then after reflection of sound wave, the number of beats per second heard by the passengers in the bus will be ______.

Options

• 5

• 6

• 2

• 4

Answer 1

A bus is moving with a velocity of 5 m is towards a wall. The driver blows the horn of frequency 165 Hz. If the speed of sound in air is 335 m is, then after reflection of sound wave, the number of beats per second heard by the passengers in the bus will be 5.

Explanation:

Frequency received by the wall v₁ = `165 (335/(335 - 5))`

`= (165 xx 335)/330`

= 167.5 Hz

Frequency of the reflected wave received by the driver v₂ = `167.5((335 + 5)/335)`

`= (167.5 xx 340)/335`

= 170 Hz

∴ Beat frequency = 170 - 165 = 5 Hz