A train running at `108 km h^-1 towards east whistles at a dominant frequency of 500 Hz. Speed of sound in air is 340 m/s. What frequency will a passenger sitting near the open window hear ? (b) What frequency will a person standing near the track hear whom the train has just passed ? (c) A wind starts blowing towards east at a speed of 36 km h-1. Calculate the frequencies heard by the passenger in the train and by the person standing near the track.

Answer

A, B, C, D

Explanation

a. velocity of passenger with respect to the train is zero.
so, required frequency =500Hz
b. Frequency heard by the person standing near the track
`n=(v+v_0)/(v+v_s)xxn_0`
`=(340+0)/(340+30)xx500=459Hz`
c. When the wind starts blowing towards east.
Frequency heard by passenger is uN/Affected.
But frequency heard by person standby near the track
`n=((v-v_(air))/((v-v_(air)v_s))xxn_0`
`=((340-10))/((340-10)+30)xx500`
`=458Hz`