A source of sound A emitting waves of frequency 1800 ~Hz is falling towards ground with a terminal speed v . The observer B on the ground directly beneath the source receives waves of frequency 2150 ~Hz . The source A receives waves, reflected from ground of frequency nearly: (Speed of sound =343 ~m / s )

Step-by-step solution

Given f _ A =1800 ~Hz aligned & v _ t = v & f _ B =2150 ~Hz aligned Reflected wave frequency received by A , f _ A ^ = ? Applying doppler's effect of sound, f ^ = v _ s f v _ s - v _ t Here, v _ t = v _ s (1- f _ A f _ B )=343 (1- 1800 2150 ) v _ t =55.8372 ~m / s Now, for the reflected wave, aligned & f _ A ^ = ( v _ s + v _ t v _ s - v _ t ) f _ A &= ( 343+55.83 343-55.83 ) 1800 &=2499.44 2500 ~Hz aligned