A train is moving at `30ms^(-1)` in still air. The frequency of the locomotive whistle is 500 Hz and the speed of sound is `345ms^(-1)`. The apparent wavelength of sound in front of and behind the locomotive are respectively

Options

A. A)0.80 m, 0.63 m
B. B)0.63 m, 0.80 m
C. C)0.50 m, 0.85 m
D. D)0.63 m, 0.75 m

Answer

D

Explanation

Apparent wavelength, in front of locomotive
`lambda.=(lambda(v-v_(s)))/(v)`
or `lambda.=(v-v_(s))/(v)`
`=(345-30)/(500)`
`=(315)/(500)=0.63m`
Behind locomotive,
`lambda..=(lambda(v+v_(s)))/(v)`
`=(v+v_(s))/(v)`
`=(345+30)/(500)`
`=(375)/(500)=0.75m`