In a double-slit experiment the angular width of a fringe is found to be `0.2^(0)` on a screen placed 1 m away. The wavelenght of light used is 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water? Take refractive index of water to be `4"/"3`.

Explanation

To solve the problem, we need to determine the angular width of the fringe when the experimental apparatus is immersed in water. Here are the steps to find the solution:

### Step 1: Understand the given data
- Initial angular width of the fringe, \( \theta = 0.2^\circ \)
- Distance from the slits to the screen, \( L = 1 \, \text{m} \)
- Wavelength of light in air, \( \lambda = 600 \, \text{nm} = 600 \times 10^{-9} \, \text{m} \)
- Refractive index of water, \( \mu = \frac{4}{3} \)

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