When a compact disc is illuminated by a source of white light, coloured lines are observed. This is due to

Options

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

Answer

To solve the question regarding the observation of colored lines when a compact disc is illuminated by white light, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Compact Disc Structure**:
- A compact disc (CD) has a surface that contains many small pits arranged in a specific pattern. These pits are responsible for storing data.

2. **Incident White Light**:
- When white light (which contains all colors of the spectrum) strikes the surface of the CD, it interacts with these pits.

3. **Diffraction Grating Effect**:
- The arrangement of pits on the CD acts like a diffraction grating. A diffraction grating is an optical component with a periodic structure that splits and diffracts light into several beams.

4. **Diffraction of Light**:
- As the white light hits the pits, it gets diffracted. Different colors (wavelengths) of light are diffracted at different angles due to their varying speeds in the medium.

5. **Observation of Colors**:
- When we look at the CD from different angles, we observe different colors because each color is diffracted at a specific angle. This results in the appearance of colored lines or patterns on the surface of the CD.

6. **Conclusion**:
- The phenomenon observed (colored lines on the CD) is primarily due to diffraction of light. Therefore, the correct answer to the question is that the colored lines are observed due to diffraction.

### Final Answer:
The colored lines observed when a compact disc is illuminated by a source of white light are due to **diffraction**.

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