A source producing sound of frequency 170 Hz is approachig a stationary observed with a velocity of `17ms^-1`. The apparent change in the wavelength of sound heard by the observer is (speed of sound in air =`340ms^-1`)

Options

A. 0.1 m
B. 0.2 m
C. 0.4 m
D. 0.5 m

Answer

A

Explanation

Apparent frequency ,`n'=n(v/(v-v_s))`
`v=340ms^-1` and `v_s=17ms^-1` ,n = 170
`n'=170xx(340/(340-17))` =179 Hz
Initial wavelength ,`lambda_1=v/n=340/170=2m`
Final wavelength,`lambda_2=v/n'=340/179=1.9m`
Change in wavelength = 2-1.9 =0.1m