Diffraction of light is observed only, when the obstacle size is-

Options

A. very large
B. very small
C. of the same order that of wavelength of light
D. any size

Answer

To solve the question regarding the conditions under which diffraction of light is observed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Diffraction**:
- Diffraction is the bending of waves around obstacles and openings. It is a phenomenon that occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength.

2. **Identifying Key Parameters**:
- The key parameters involved in diffraction are the wavelength of the light (λ) and the size of the obstacle or aperture (d).

3. **Comparative Size Requirement**:
- For significant diffraction to occur, the size of the obstacle (d) must be comparable to the wavelength of the light (λ). This means that the size of the obstacle should be on the same order of magnitude as the wavelength.

4. **Mathematical Relation**:
- The relationship can be expressed as:
\[ d \approx \lambda \]
- This indicates that when the size of the obstacle is approximately equal to the wavelength, diffraction effects will be pronounced.

5. **Conclusion**:
- Therefore, the conclusion is that diffraction of light is observed when the size of the obstacle is of the same order as the wavelength of the light.

### Final Answer:
The size of the obstacle should be comparable to the wavelength of light for diffraction to be observed.