A source of short sound signals is located on the surface of the lake. The receiver of sound signals is located

A source of short sound signals is located on the surface of the lake. The receiver of sound signals is located h = 30m below the source on the same vertical line with it. The sound signal reflected from the flat bottom is registered by the receiver in T = 60ms after its sending. Determine the depth of the lake at this location. The speed of sound in water is taken equal to Ʋ = 1500 m / s.

During the time T = 60 ms, the sound signal travels the distance:
H + (H-h) where H is the depth of the lake, h = 30 m.
Then we get the equation:
H + (H-h) / U = T, where U is the speed of sound.
From here we get:
2H-h = TU
2H = TU-h
H = (T * U-h) / 2 = (1500 * 60 * 10 ^ -3-30) / 2 = (90-30) / 2 = 60/2 = 30 m.