Soap Bubbles Contact Interface – Rankers Physics

Surface Tension and Viscosity: Practice Problem & Solution

Given below are two statements: Assertion (A): When two soap bubbles of different radii are brought into contact, the common interface of contact bulges into the bubble of larger radii. Reason (R): Pressure inside a soap bubble of a lesser radius is more than pressure inside the soap bubble of a larger radius.  
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of (A).
(A) is true but (R) is false.
Both (A) and (R) are false.

Solution Explained:

To solve this problem, we apply the core principles of Surface Tension and Viscosity. Understanding the underlying formula is key to arriving at the correct answer below:

The excess pressure inside a soap bubble is \(P = \frac{4T}{R}\). Thus, pressure is greater inside the smaller bubble (lesser radius). When in contact, the common interface bulges towards the larger bubble due to this pressure difference. Both are true and Reason explains Assertion.

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