A road runs parallel to a vertical cliff at a distance of 495 m as shown in the figure . A car standing at A blows the horn and the driver of the car hears the echo after 3 s. But a person standing at B hears the sounds of horn twice within an interval of 2s .
Explain why the person at 'B' heard the sound twice . Also find the distance between the car and the person .

Explanation

(i) Equation of echo , Pythagoras theorem
(ii) `v = (2d)/(t_(1))`
`v = (("distance covered by sound waves") + ( "distance between driver and person"))/(t_(2))`
Pythagoras theorem
(iii) 412 m