A bubble of gas released at the bottom of a lake increases to eight times its original volume when it reaches the surface. Assuming that atmospheric pressure is equivalent to the pressure exerted by a column of water 10 m height, the depth of the lake is

Options

A. 80 m
B. 90 m
C. 40 m
D. 70 m

Answer

D

Explanation

As volume of the bubble at the surface becomes 8 times, pressure at the bottom of the lake is 8 times the pressure at the surface. As pressure on the surface =1 atm., pressure at the bottom =8 atm. Thus, pressure due to depth of the lake =7 atm=70 m of water.