In a Young's double-slit experiment apparatus, we use white light. Then

Options

A. The fringe next to the central will be red
B. The central fringe will be white
C. The fringe next to the central will be violet
D. There will not be a completely dark fringe

Answer

**Step-by-Step Solution:**

1. **Understanding the Setup**: In a Young's double-slit experiment, white light is used as the source. White light consists of multiple wavelengths corresponding to different colors (red, orange, yellow, green, blue, indigo, violet).

2. **Central Maximum**: At the center of the screen (point O), the path difference between the light coming from the two slits is zero. This means all wavelengths constructively interfere at this point, resulting in a bright white fringe at the center.

3. **Fringe Formation**: As we move away from the center, different wavelengths will have different path differences. The fringe pattern will be formed due to constructive and destructive interference of the different wavelengths.

4. **Color Sequence**: The fringe next to the central maximum will be the first order maximum for the shortest wavelength (violet) and will be closest to the center. As we move outward, the sequence of colors will be violet, blue, green, yellow, orange, and red. Thus, the fringe next to the central maximum will be violet.

5. **Colorful Pattern**: Since white light contains all colors, the interference pattern will not be monochromatic. Instead, it will be colorful, with the central maximum being white and the fringes displaying a spectrum of colors.

6. **Conclusion**: The correct observations from the experiment are:
- The central fringe is white.
- The fringe next to the center is violet.
- The pattern will be colorful, not completely dark.

**Final Answer**: The correct options are 2 (the fringe next to the center will be violet), 3 (the central fringe will be white), and 4 (the pattern will be colorful).

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