Question

As an air bubble rises from the bottom of a lake to the surface, its volume is doubled. Find the depth of the lake. Take atmospheric pressure = 76 cm of Hg.

Answer 1

Correct Answer - `10.34 m`
As volume of air bubble becomes double on reaching the surface of lake, hence its pressure becomes half. Since on the lake, the pressure is equal to the atmospheric pressure, hence the pressure of air inside the bubble at the depth of lake = 2 atmospheric pressure = atmospheric pressure + pressure due to column of water h. thus
`2 xx 76 cm of Hg = 76 cm of Hg + h cm` of water`
or `76 cm of Hg = h cm` of water
of Depth of lake `= 76 cm of Hg`
`=76 xx 13.6 cm of water`
`=1033.6 cm = 10.34 m`