A train is approaching towards a platform with a speed of ( 10 ~ms ⁻¹ ) while blowing a whistle of frequency ( 340 ~Hz ). What is the frequency of whistle heard by a stationary observer on the platform ? Given speed of sound ( =340 ~ms ⁻¹ ).

Step-by-step solution

According to Doppler effect there is a change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source, which is given as ( f^ = ( v v-v_ s ) f ) where ( f ^ ) is the apparent frequency; ( f ) is frequency of source; ( v_ S ) is velocity of source; ( v ) is velocity of sound Given ( f=340 H z ; v=340 ~ms ⁻¹ ; v_ s =10 ~ms ⁻¹ ) Therefore, ( f^ = ( 340 340-10 ) 340=350.3030 H z 350 H z ) Thus, frequency of whistle heard by a stationary observer on the platform is ( 350 ~H