If a soap bubble expands, the pressure inside the bubble:

CONCEPT:

In a liquid drop, we have only one surface but in the air bubble we have two surfaces and a mathematical expression of the excess pressure inside an air bubble and inside the liquid drop by using the concept of surface tension is written as;

P_i - P_o = \(\frac{4T}{r}\)

Here, P_i and P_o are the pressure inside and outside, T is the temperature and r is the radius.

EXPLANATION:

As we know that the pressure of the soap bubble is written as;

Pi - Po = \(\frac{4T}{r}\) ---(1)

When the soap bubble expands the radius of the soap bubble will increase, therefore from equation (1) we see that the change in pressure is inversely proportional to the radius of the soap.

∴ soap bubble expands the radius will increases and inside pressure will decrease.

Hence option 2) is the correct answer.