Question

The property of light which cannot be explained by Huygen's construction of wavefront is:

• A. Refraction
• B. Reflection
• C. Diffraction
• D. Origin of spectra

Hint:

Huygen's principle is extremely useful in understanding the behavior of light in terms of wave propagation, but keep in mind that it cannot fully explain certain quantum mechanical phenomena such as the origin of spectra.

Answer 1

The Correct Option is D

Huygen's principle is used to explain the wave nature of light, including phenomena such as refraction, reflection, and diffraction. However, it cannot explain the origin of spectra, as it primarily deals with wavefronts and their propagation. The origin of spectra, such as in the case of emission and absorption lines, is a quantum mechanical phenomenon and is not explained by Huygen's principle.

Answer 2

Step 1: Understand Huygen’s principle.
Huygen’s principle explains the propagation of light waves by considering every point on a wavefront as a source of secondary spherical wavelets. The new wavefront is found by drawing a surface tangent to these wavelets.

Step 2: Phenomena explained by Huygen’s construction.
Using Huygen’s wavefront construction, we can explain several wave-like properties of light such as:
- Reflection
- Refraction
- Diffraction
- Interference

Step 3: What Huygen’s theory cannot explain.
Huygen’s wave theory is a classical theory and does not address the quantum nature of light.
The origin of spectra (such as atomic emission or absorption lines) is explained using quantum mechanics, which considers the transitions of electrons between discrete energy levels in atoms—something Huygen’s theory does not account for.

Step 4: Conclusion.
The property of light which cannot be explained by Huygen’s construction of wavefront is origin of spectra.
Hence, the correct answer is: \( \boxed{\text{Origin of spectra}} \)