A ray of light travelling straight bends by a small but fixed angle. It may be due to

Options

A. Reflection
B. Refraction
C. Dispersion
D. Diffraction

Explanation

To solve the question "A ray of light travelling straight bends by a small but fixed angle. It may be due to...", we need to analyze the possible phenomena that can cause a light ray to bend. The options we will consider are reflection, refraction, dispersion, and diffraction.

### Step-by-Step Solution:

1. **Understanding the Scenario**:
- A ray of light is traveling straight and then bends by a small but fixed angle. This indicates that there is a change in direction of the light ray.

2. **Analyzing Reflection**:
- When light hits a reflective surface (like a mirror), it can change direction. According to the law of reflection, the angle of incidence is equal to the angle of reflection. If the surface is flat, the bending of the ray can be considered a fixed angle.
- Conclusion: Reflection can cause the ray to bend by a fixed angle.

3. **Analyzing Refraction**:
- Refraction occurs when light passes from one medium to another (for example, from air to glass). The light ray bends at the interface according to Snell's law, which relates the angles of incidence and refraction to the indices of refraction of the two media.
- If the angle of incidence is small and the indices of refraction are known, the angle of refraction can also be determined, thus making it a fixed angle.
- Conclusion: Refraction can also cause the ray to bend by a fixed angle.

4. **Analyzing Dispersion**:
- Dispersion occurs when light passes through a prism and different wavelengths (colors) of light bend by different amounts. This results in a spectrum of colors and not a single fixed angle.
- Conclusion: Dispersion does not cause a fixed angle of bending.

5. **Analyzing Diffraction**:
- Diffraction occurs when light passes through a small aperture or around an obstacle, causing the light to spread out and create interference patterns. This results in multiple rays and does not produce a single fixed angle of bending.
- Conclusion: Diffraction does not result in a fixed angle of bending.

6. **Final Conclusion**:
- Based on the analysis, the bending of a ray of light by a small but fixed angle can be attributed to either reflection or refraction. Therefore, the correct answer to the question is that the bending may be due to reflection or refraction.