A bat emitting an ultrasonic wave of frequency 4.5 × 104 Hz flies at a speed of 6 rn/s between two parallel walls. Find the two frequencies heard by the bat and the beat frequency between the two. The speed of sound is 330 m/s.

Let us assume that the bat is flying from wall B to wall A.


The given parameters are,


Vs=6ms-1


f0=4.5x104 Hz


The apparent frequency received by wall A will be,





Now the wall A will act like a source and the bat is moving towards A. So, the apparent frequency will be,





Now the apparent frequency received by the wall B will be,






Now, wall be will act like a source and the apparent frequency received by the bat will be,






Now the beat frequency will be,




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