Question

When a bubble, released from the bottom of a lake, rises near the water surface, it

• A. increases in volume
• B. decreases in volume
• C. does not change volume
• D. decreases in radius

Answer 1

The correct option is A increases in volume

The pressure at a depth in a liquid is given by $P_0+\rho gh$ where $P_0$ is the pressure at the surface, $\rho$ is the density of the liquid, and $h$ is the depth from the surface of the water.
The pressure in a bubble is given by $P=P_0+\frac{2T}{R}$,
where {P}_{0} = Atmospheric pressure; T = surface tension; R = radius of the bubble
In order for the gas bubble to be at equilibrium, the pressure inside the bubble should be equal to the pressure of the liquid. As the gas bubble rises, $h$ decreases and hence the pressure decreases.
Therefore, the pressure inside the bubble should also decrease => $R$ increases.