In YDSE performed with wavelength `lambda = 5890 Å` the angular fringe width is `0.40^(@)`. What is the angular fringe width if the entire set-up is immersed in water?

Explanation

To solve the problem, we need to determine the angular fringe width when the Young's double slit experiment (YDSE) is performed in water. Here's a step-by-step solution:

### Step 1: Understand the relationship between fringe width and wavelength
In YDSE, the angular fringe width (θ) is given by the formula:
\[ \beta = \frac{\lambda}{d} \]
where:
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