Wave theory cannot explain the phenomena of
A. Interference
B. Diffraction
C. Compton effect
D. Photoelectric effect
Which of the following is correct?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C and D
Light shows a dual nature. The wave picture explains effects in which waves overlap and spread. Effects in which radiation gives energy and momentum to electrons need the photon picture.
A. Interference — Explained by wave theory. The bright and dark fringes come from the superposition of waves that arrive in phase or out of phase.
B. Diffraction — Explained by wave theory. The bending of light round the edges of an obstacle or aperture is a wave effect.
C. Compton effect — Not explained by wave theory. In the scattering of X-rays from electrons, the radiation gives energy and momentum to the electrons as particles (photons) would.
D. Photoelectric effect — Not explained by wave theory. Emission needs light above a threshold frequency, whatever its intensity, and it starts at once. Each photon gives its energy \( h\nu \) to one electron.
NCERT (2026-27):
Wave Nature of Matter – “The dual (wave-particle) nature of light (electromagnetic radiation, in general) comes out clearly from what we have learnt in this and the preceding chapters. The wave nature of light shows up in the phenomena of interference, diffraction and polarisation. On the other hand, in photoelectric effect and Compton effect which involve energy and momentum transfer, radiation behaves as if it is made up of a bunch of particles – the photons.”