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 of finding the change in the focal length of a convex lens when it is immersed in water, we will follow these steps:

### Step 1: Understand the given data
- Refractive index of the lens (n_lens) = 1.5
- Focal length of the lens in air (f_air) = 20 cm
- Refractive index of water (n_water) = 4/3

### Step 2: Use the Lensmaker's Formula
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