Question

A person clapped his hands near a cliff and heard the echo. The minimum distance of the cliff from the person if the speed of sound is taken as 346 m/s is

• A. 17.1 m
• B. 17.2 m
• C. 17.3 m
• D. 34.6 m

Answer 1

The correct option is C 17.3 m

The minimum time difference between actual sound and hearing its echo should be atleast 0.1 s so that the brain is able to discern the sounds as seperate sounds, therefore

$V=\frac{2d}{t}$
$t=0.1s$
$346=\frac{2d}{0.1}\Rightarrow d=\frac{34.6}{2}=17.3m$