A convex lens of refractive index 1.5 has a focal length of 20 cm in air. Calculate the change in its focal length when it is immersed in water of refractive index 4/3.

Explanation

To solve the problem step by step, we will follow these steps:

### Step 1: Write down the given data
- Refractive index of the lens (glass), \( \mu_g = 1.5 \)
- Focal length of the lens in air, \( F_A = 20 \, \text{cm} \)
- Refractive index of water, \( \mu_w = \frac{4}{3} \)

### Step 2: Use the lens maker's formula for the lens in air
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