Two factories are sounding their sirens at 800 Hz. A man goes from one factory to the other at a speed of 2 m/s. The velocity of sound is 320 m/s. The number of beats heard by the person is 1 s will be

Explanation

Here, `v=800Hz, v_(L)=2m//s, upsilon=320m//s.`
Number of beats `//` sec. `m=?`
The man moves from one factory to the other. The apparent frequency of siren heard from the factory from which he is moving away
`v_(1)=((upsilon-upsilon_(L))v)/(upsilon)=((320-2)800)/(320)=(318)/(320)xx800Hz`
The apparent frequency of siren heard from the factory to which the man is moving.
`v_(2)=((upsilon+upsilon_(L))v)/(upsilon)=((320+2)800)/(320)=(322)/(320)xx800Hz`
`:. ` Number of beats heard per sec., `m=v_(2)-v_(1)`
`=(322)/(320)xx800-(318)/(320)xx800`
`=(800)/(320)(322-318)`
`m=(800xx4)/(320)=10`