A bat emitting an ultrasonic wave of frequecy `4.5 xx 10^4` Hz flies at a speed of `6ms^(-1)` between two parallel walls. Find the two frequecies heard by the bat and the beat frequecy between the two. The speed of sound is `330ms^(-1)`

Answer

A, B, C, D

Explanation

Let the bat be flying between three walls `W_1W_2.` so it will listen two frequecny reflecting from walls `W_2 and W_1` So, appernt frequency, as received by well W,
`W_2 = ((330 + 0+0)/(330 - 0.6))xx f = (330)/(324)`
There, fore app. frequency received by the bat from wall `W_2` is given by
`F_(B2) at wall w_1`
`=((330 + 0- (-6))/(330 + 0 +0))f_1 W_2`
`=((336)/(330))xx((330)/(324))f`
Similarly, the apperent frequency recevied by the bat from wall `W_1` is,
`f_(B1) = ((324)/(336))f`
so the beat frequency head by the bat
`= 4.67 xx 10^4 - 4.3430 xx 10^4`
=3270 Hz.