Question

A person standing symmetrically between two cliffs claps his hands and starts hearing series of echoes at intervals of 1 sec. If speed of sound in air is 340 m/s, the distance between the parallel cliff must be

• A. 340 m
• B. 680 m
• C. 1020 m
• D. 170 m

Answer 1

Answer: (A)

340 m

Let x be distance of person from each cliff

$\therefore x+x=v\times t=340\times 1=340$

$x=170m$

Distance between two cliffs $=2\times 170=340m$