Which of the following phenomena cannot be explained by wave theory of light?

Solution

Physics sir · 4 steps

Reflection, refraction and diffraction are wave stories; Compton scattering needs light as a particle.

1. Wave explanations. Reflection and refraction follow from Huygens' wavefronts changing direction at a surface. Diffraction is waves bending around an obstacle or slit.
2. Compton effect. When X-rays scatter off electrons, the scattered rays have a longer wavelength, and the shift depends on the scattering angle. A classical wave would make the electron oscillate at the same frequency, so it would re-radiate at the same wavelength.
3. Photon picture. Treat the X-ray as a photon with energy hν and momentum h/λ that collides with an electron. Energy and momentum conservation give the shift exactly.

   Δλ = h/(mₑ c)(1-cos θ)

4. So. Only the Compton effect needs the particle (photon) nature of light, so the answer is (d).

The idea to keep. If light exchanges energy and momentum in packets, as in the photoelectric effect and the Compton effect, you need photons. Bending and spreading, as in interference and diffraction, are wave behaviour.

Answer from the NTA final answer key. Solution by PrepWiser.