A beam of light consisting of wavelengths 6000 `Å` and 4500 `Å` is used in a YDSE with D = 1 m and d = 1 mm. Find the least distance from the central maxima, where bright fringes due to the two wavelengths coincide.

Explanation

To solve the problem, we need to find the least distance from the central maxima where bright fringes due to two different wavelengths coincide in a Young's Double Slit Experiment (YDSE). Let's break down the steps:

### Step 1: Understand the formula for fringe positions
In YDSE, the position of the bright fringes is given by:
\[ y_n = \frac{n \lambda D}{d} \]
where:
- \( y_n \) = position of the nth bright fringe,
- \( n \) = order of the fringe (1, 2, 3,...),
...