An air bubble doubles its radius on raising from the bottom of water reservoir to the surface of water in it. If the atmosphetic pressure is equal to 10 m of water, the height of water in the reservoir will be

Options

A. 10 m
B. 20 m
C. 70 m
D. 80 m

Answer

C

Explanation

`(P_1V_1)_"bottom"=(P_2V_2)_"top"" [Boyle.s law]"`
`(10+h)xx4/3pir_1^3=10xx4/3pir_2^3" but "r_2=2r_1`
`therefore(10+h)r_1^3=10xx8r_1^3rArr10+h=80`
`thereforeh=70m`