Question

A railroad train is travelling at 30 m/s in still air. The frequency of the note emitted by the locomotive whistle is 500 Hz. The wavelength of the sound waves in front of locomotive is $628\times {10}^{-x}m$. Find x.

Answer 1

Apparent wavelength ${\lambda }^{\prime }$ of sound , when source of sound is approaching to a stationary observer is given by ,

${\lambda }^{\prime }=(v-v_s/f)$

λ′=vf.(v+vsv)

where

$v_s=$speed of source ,

v=v= speed of sound ,

f=f= frequency of sound ,

given v=344m/s,vs=30m/s,f=500Hzv=344m/s,vs=30m/s,f=500Hz ,

therefore , ${\lambda }^{\prime }=344-30/500=0.628m$