• Subject:


  • Topic:


A train moving at a speed of 220 ms-1

towards a stationary object, emits a sound 

of frequency 1000 Hz. Some of the sound 

reaching the object gets reflected back to 

the train as echo. The frequency of the echo

as detected by the driver of the train is

(speed of sound in air is 330 ms-1)

(a) 3500Hz

(b) 4000Hz

(c) 5000Hz

(d) 3000Hz