Question

calculate the minimum distance in air between the source of sound and obstacle to hear an echo . Speed = 350 m /s

Answer 1

The sensation of sound persists in our brain for about 0.1 s.

i.e to hear a distinct echo the minimum time interval between the original sound and the reflected sound = 0.1s.

V = 350 m/s (Given)

t = 0.1 s

d = (V*t)/2

d = (350*0.1)/2 = 17.5 m