Red light of wavelength 6000 Å is used in a Young's double-slit experiment. At a point P on the screen `n^(th)` bright fringe is obtained . When red light is replaced with blue light of wavelengh `4000 Å, ( n + 1)^(th)` bright fringe is obtained at the same point P. Calculate the value of n.

Explanation

To solve the problem, we will use the principles of interference in a Young's double-slit experiment. Let's break down the solution step by step.

### Step 1: Understand the setup
In a Young's double-slit experiment, the position of bright fringes on the screen is given by the formula:
\[ y_n = \frac{n \lambda D}{d} \]
where:
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