A thin lens `(mu = 1.5)` of focal length + 12 cm is immersed in water `(mu = 1.33).` What is its new focal length ?

Explanation

To find the new focal length of a thin lens immersed in water, 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:

\[ \frac{1}{f} = \left(\frac{\mu_l}{\mu_m} - 1\right) \left(\frac{1}{r_1} - \frac{1}{r_2}\right) \]
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