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, when a monochromatic source is replaced with white light, the interference pattern changes due to the composition of white light, which consists of multiple wavelengths.

• Central Fringe: The central fringe will be bright and white because every wavelength of light is in-phase at the center, resulting in constructive interference.
• Surrounding Fringes: As you move away from the center, different wavelengths recombine differently, leading to dispersion and the formation of colored fringes. Each color corresponds to a different wavelength experiencing constructive or destructive interference at various points.

Therefore, the correct answer is that there will be a central bright white fringe surrounded by a few colored fringes.

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.