Question

A boy stands facing a high wall at a distance of 85 m from it and then blows a whistle. Calculate the time interval when he hears an echo (Speed of sound = 340 m $s^{-1}$).

• A. 1s
• B. 2s
• C. 0.5 s
• D. 3s

Answer 1

The correct option is C 0.5 s

Given,

Distance, $d=85m$

Speed of sound, $v=340m{s}^{-1}$

We have to find the time period $t$

Total distance travel by sound wave to hear echo $=2d$

We have the equation,

$v=\frac{Distancetravel}{Timeconsumed}=\frac{2d}{t}$

Then,

$t=\frac{2d}{v}=\frac{2\times 85}{340}=\frac{170}{340}=0.5s$