Question

The minimum distance of reflector surface from the source for listening the echo of sound is :

• A. 28 m
• B. 18 m
• C. 16.5 m
• D. 12 m

Answer 1

The correct option is C 16.5 m

$\left(c\right)2d=v\times t,$ where $v=$ velocity of sound $=332m/s$

$t=$ Persistence of hearing $=\frac{1}{10}sec$

$\Rightarrow d=\frac{v\times t}{2}=\frac{332\times \frac{1}{10}}{2}=16.5m$