An engine blowing a whistle of frequency 133 Hz moves with a velocity of `60(m)/(s)` towards a wall from which an echo is heard. Calculate the frequency of the echo heard by the driver. (velocity of sound in air in `340(m)/(s)`.)

Explanation

The image of the source approaches the driver at the same speed here the image or echo is the source Therefore.
`v_S=+60(m)/(s)`,`v_0=-60(m)/(s)`
`n'=(c-v_0)/(C-v_S)xxn`
`n'=(340-(-60))/(340-60)xx133implies'=190Hz`