Which of the following phenomenon is not explanined by Huygen's construction of wavefront ?

Options

A. Refractin
B. Reflection
C. Diffraction
D. Origin of spectra

Answer

To determine which phenomenon is not explained by Huygen's construction of wavefront, we need to understand what Huygen's principle entails and which phenomena it can and cannot explain.

### Step-by-Step Solution:

1. **Understanding Huygen's Principle**:
Huygen's principle states that every point on a wavefront can be considered as a source of secondary wavelets that spread out in all directions at the speed of the wave. The new wavefront is then formed by the envelope of these secondary wavelets.

2. **Identifying the Phenomena**:
We need to analyze the options provided (though they are not listed in the question) to see which phenomena can be explained by Huygen's principle. Common phenomena explained by Huygen's principle include:
- Reflection
- Refraction
- Diffraction

3. **Analyzing Each Option**:
- **Reflection**: Huygen's principle can explain reflection as it shows how wavefronts change direction upon hitting a reflective surface.
- **Refraction**: It can also explain refraction as it describes how wavefronts bend when they pass from one medium to another.
- **Diffraction**: Huygen's principle accounts for diffraction, illustrating how waves spread out after passing through narrow openings or around obstacles.

4. **Identifying the Exception**:
The question asks for a phenomenon that is NOT explained by Huygen's principle. One such phenomenon is the **origin of spectra**. Huygen's principle does not explain how different wavelengths of light are produced or how they originate.

5. **Conclusion**:
Based on the analysis, the phenomenon that is not explained by Huygen's construction of wavefront is the **origin of spectra**.

### Final Answer:
The phenomenon that is not explained by Huygen's construction of wavefront is the **origin of spectra**.