Question

An air bubble doubles its volume as it rises from the bottom of a tank to its surface. if the atmospheric pressure be 76cmof hg what is the depth of the tank

Answer 1

We know that 

P1V1 = P2V2

So pressure is directly proportional to volume

So if pressure increase volume increases and vice versa. 


At the bottom of a lake the pressure is very height due to depth and low temperature. 

When the bubble rises at the surface the pressure gradually decreases and hence  volume increases