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If a soap bubble expands, the pressure inside the bubble

Asked in NEET 2022 · Excess pressure

Answer: (1) decreases

Step-by-step solution

Given: a soap bubble of radius R blown from a solution of surface tension T.

Idea: a soap bubble has two liquid surfaces, so the pressure jump across its wall is twice that of a single drop.

Pᵢₙ=P₀+(4T)/R

T is fixed by the solution and P₀ by the room, so only R changes.

As the bubble expands R grows and (4T)/R falls.

Hence the pressure inside decreases, approaching P₀ from above.

Why the other options are wrong

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