How does the fringe width of interference fringes change, when the whole apparatus of Young's experiment is kept in a liquid of refractive index 1.3 ?

Explanation

To solve the problem regarding how the fringe width of interference fringes changes when the whole apparatus of Young's experiment is placed in a liquid of refractive index 1.3, we can follow these steps:

### Step 1: Understand the Fringe Width Formula
The fringe width (β) in Young's double-slit experiment is given by the formula:
\[ \beta = \frac{\lambda D}{d} \]
where:
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