A soap bubble of radius r si blown up to form of bubble of radius 3r under isothermal conditions . What is the energy spent in doing so if the surface tension of soap solution is S.

Explanation

To find the energy spent in blowing up a soap bubble from radius \( r \) to radius \( 3r \) under isothermal conditions, we can follow these steps:

### Step 1: Understand the surface area change
The surface area \( A \) of a sphere is given by the formula:
\[ A = 4\pi r^2 \]
For the initial bubble of radius \( r \), the surface area \( A_i \) is:
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