A sound source, fixed at the origin, is continuously emitting sound at a frequency of 660 Hz. The sound travels in air at a speed of `330 ms^-1`. A listener is moving along the line x = 336 m at a constant speed of 26 m Find the frequency of the sound as observed by the listener when he is a. at `y=-140m, b. at y=0 and c. at y=140m`.

Answer

A, B, C, D

Explanation

a. Frequency at `y=140 m is
`n=(v+v_0)/(v-v_s)n_0`
`=(330+26xx(140/364))/330=660`
`=340xx5=680 Hz` b. When y=0 velocity of observer with respect to source is zero.
so, required frequency =660 Hz
c. When y=140 m `
`n=(v-v_0)/vxx660`
`=(330-((26xx140)/364))/330xx660`
`=(330-10)/330xx660=640Hz`