A thin lens of refractive index `1.5` has focal length of `15 cm` in air. When the lens is placed is a medium of refractive index (4)/(3), its focal length will become …..cm.

Explanation

To find the new focal length of a thin lens when it is placed in a medium with a different refractive index, we can use the lens maker's formula. Let's go through the solution step by step:

### Step 1: Understand the Lens Maker's Formula
The lens maker's formula is given by:
\[ \frac{1}{f} = \left( \frac{\mu - 1}{n} \right) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \]
where:
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