Question

If the monochromatic source in Young's double slit experiment is replaced by white light,
1. There will be a central dark fringe surrounded by a few coloured fringes
2. There will be a central bright white fringe surrounded by a few coloured fringes
3. All bright fringes will be of equal width
4. Interference pattern will disappear

• A. interference pattern will disappear.
• B. there will be a central dark fringe surrounded by a few coloured fringes
• C. there will be a central bright white fringe surrounded by a few coloured fringes.
• D. all bright fringes will be of equal width

Answer 1

The Correct Option is C

In Young's double slit experiment, if white light is used in place of monochromatic light, then the central fringe is white and some coloured fringes around the central frings are formed.

Since βred>βvio≤t etc., the bright fringe of violet colour forms first and that of the red forms later.
It may be noted that the inner edge of the dark fringe is red, while the outer edge is violet. Similarly, the inner edge of the bright fringe is violet, and the outer edge is red.
 

Answer 2

Interference with White Light in Young's Double-Slit Experiment 

Step 1: Understand the Nature of Interference with White Light

White light consists of multiple wavelengths. In Young’s double-slit experiment, each wavelength creates its own interference pattern.

Step 2: Analyze the Central Fringe

At the center (x = 0), all wavelengths interfere constructively, producing a bright white fringe.

Step 3: Analyze the Surrounding Fringes

For higher orders, different wavelengths interfere differently, leading to overlapping colored fringes.

Step 4: Conclude

The central fringe is bright white, and a few colored fringes appear around it.