What happens by the use of white light in Young's double slit experiment:

Options

A. Bright fringe are obtained
B. Only bright and dark fringes are obtained
C. Central fringes is bright and two or three coloured and dark fringes are observed
D. none of the above

Answer

To solve the question regarding the use of white light in Young's double slit experiment, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Setup**:
- In Young's double slit experiment, two slits (let's call them H1 and H2) are illuminated by a coherent light source. The light passing through these slits creates an interference pattern on a screen.

2. **Using White Light**:
- White light is composed of multiple colors (spectrum) ranging from red to violet. When white light passes through the slits, each color has a different wavelength.

3. **Central Fringe**:
- At the center of the screen (point O), the path difference between the light coming from the two slits is zero. This means that the phase difference is also zero, leading to constructive interference. Therefore, the central fringe is bright.

4. **Colored Fringes**:
- As we move away from the center, the path difference increases, leading to varying degrees of constructive and destructive interference for different colors. This results in colored fringes being observed. The first few fringes on either side of the central bright fringe will show colors due to the different wavelengths of light.

5. **Formation of Dark Fringes**:
- Further away from the center, as the path difference continues to increase, there will be positions where destructive interference occurs for certain colors, leading to dark fringes. This means that at some points, the light waves from the two slits cancel each other out.

6. **Conclusion**:
- Therefore, in Young's double slit experiment with white light, we observe a central bright fringe, followed by several colored fringes, and then dark fringes as we move further away from the center.

### Final Answer:
The correct observation when using white light in Young's double slit experiment is: the center fringe is bright, followed by 2 or 3 colored fringes, and dark fringes are observed further away. Thus, the answer is option C.

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