As air bubble rises from bottom to the top of a water tank. the size of the b ubble increases. It happens, because

Options

A. the pressure exerted by water on the bubble decreases as the height of the water column above it decrease
B. the density of water increases as we move downwards.
C. at constant temperature, pressure inside the air bubble are volume of the bubble inversely proportional to each other.
D. Both l and 3

Answer

To solve the question of why the size of an air bubble increases as it rises from the bottom to the top of a water tank, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Pressure in Fluids**:
- The pressure exerted by a fluid at a certain depth is given by the formula:
\[ P = P_0 + \rho g h \]
where \( P_0 \) is the atmospheric pressure, \( \rho \) is the density of the fluid (water, in this case), \( g \) is the acceleration due to gravity, and \( h \) is the depth of the fluid.

2. **Pressure Changes with Depth**:
- As the air bubble rises, the height \( h \) decreases. This means that the pressure exerted by the water on the bubble decreases as well. At the bottom of the tank, the pressure is higher due to the greater water column above it, while at the top, the pressure is lower.

3. **Gas Laws and Volume-Pressure Relationship**:
- According to Boyle's Law, for a given mass of gas at constant temperature, the pressure and volume are inversely proportional:
\[ PV = k \]
where \( k \) is a constant. This means that if the pressure \( P \) decreases, the volume \( V \) must increase to keep the product \( PV \) constant.

4. **Application of Boyle's Law to the Bubble**:
- As the bubble rises and the pressure decreases, the volume of the gas inside the bubble increases. Since the amount of air (moles of gas) inside the bubble remains constant and the temperature is assumed to be constant, the decrease in pressure leads to an increase in volume.

5. **Conclusion**:
- Therefore, the size of the air bubble increases as it rises to the top of the water tank due to the decrease in pressure exerted by the water and the inverse relationship between pressure and volume of the gas inside the bubble.

### Final Answer:
The size of the air bubble increases as it rises from the bottom to the top of a water tank because:
1. The pressure exerted by the water decreases as the bubble rises.
2. At constant temperature, the pressure inside the bubble and its volume are inversely proportional.