Question

Assertion: A bubble comes from the bottom of a lake to the top.
Reason: Its radius increases.

• A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
• B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
• C. If Assertion is true but Reason is false.
• D. If both Assertion and Reason are false.

Answer 1

Answer: (B)

Since, the fluid move from higher pressure to lower pressure and in a fluid, the pressure increase with increase of depth. Hence, the pressure $p_0$ will be lesser at the top than that at the bottom ( $p_0+h\rho g$ ). So, the air bubble moves from the bottom to the top and does not move sideways, since the pressure is same at the same level. Further in coming from bottom to top the pressure decreases. According to Boyle's law $pV=$ constant.
Therefore, if pressure decreases the volume increases, it means radius increases.