Question

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 1

Frequency received by bat after reflection from wall `①`
`f_(1) = f((v + u)/(v - u)) = (4.5 xx 10^(4)) ((330 + 6)/(330 - 6))`
`= 4.67 xx 10^(4) Hz`
Frequency received by bat after reflection from wall `②`
`f_(2) = f((v - u)/(v + u)) = (4.5 xx 10^(4)) ((330 - 6)/(330 + 6))`
`=4.34 xx 10^(4) Hz`
Beat frequency `= f_(1) - f_(2) = 3300 Hz`