For diffraction to be observed, the main condition is

Options

A. the size of an obstacle should be of the same order as the wavelength
B. the size of an obstacle should be very large as compared to the wavelength of light used
C. the size of an obstacle should be exactly `lambda//2`
D. there should be no relation between the wavelength and the size of the obstacle

Answer

To determine the main condition for diffraction to be observed, let's break down the explanation step by step.

### Step-by-Step Solution:

1. **Understanding Diffraction**:
- Diffraction refers to the bending and spreading of waves when they encounter an obstacle or pass through a narrow opening. It is a wave phenomenon observed in various types of waves, including sound and light.

2. **Key Factor in Diffraction**:
- The primary factor that influences diffraction is the relationship between the size of the obstacle (or aperture) and the wavelength of the wave.

3. **Condition for Observing Diffraction**:
- For diffraction to be prominently observed, the size of the obstacle or aperture must be comparable to the wavelength of the wave. This means that the dimensions of the obstacle should be on the same order of magnitude as the wavelength.

4. **Conclusion**:
- Therefore, the main condition for diffraction to be observed is that the size of the obstacle (or aperture) must be equal to or similar to the wavelength of the wave. This can be summarized as:
- **Condition**: Size of the obstacle ≈ Wavelength of the wave.

### Final Answer:
The main condition for diffraction to be observed is that the size of the obstacle must be of the same order as the wavelength of the wave.

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