Question

What should be the minimum distance between source and reflector in water so that echo is heard distinctly?
(The speed of sound in water = 1400 m s^-1)

Answer 1

t = 0.1 sec,

v = 1400 m/s

t = `(2d)/v`

Or d = `(tv)/2`

= `(0.1 xx 1400)/2`

= 70 m