Which of the following phenomenon can be explained by the wave picture of light
A. Photo-electric effect
B. Compton effect
C. Polarisation
D. Diffraction
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C and D only
The wave picture of light accounts for phenomena that depend on its wave properties — interference, diffraction and polarisation. Phenomena in which light exchanges energy and momentum with matter in discrete amounts need the photon picture.
(A) Photo-electric effect — Incorrect. The instantaneous emission, the threshold frequency and the independence of the electron energy from the intensity cannot be explained by waves; they need Einstein’s photon picture.
(B) Compton effect — Incorrect. The change in the wavelength of scattered X-rays is explained by treating light as photons that collide with electrons and share energy and momentum.
(C) Polarisation — Correct. It depends on light being a transverse wave, with the electric vector confined to one plane.
(D) Diffraction — Correct. The bending of light around obstacles and the fringe pattern behind a slit follow from the superposition of wavelets.
NCERT (2026-27):
Photoelectric Effect and Wave Theory of Light – “The wave nature of light was well established by the end of the nineteenth century. The phenomena of interference, diffraction and polarisation were explained in a natural and satisfactory way by the wave picture of light.”
Photoelectric Effect and Wave Theory of Light – “… These expectations of the wave theory directly contradict observations (i), (ii) and (iii) given at the end of sub-section 11.4.3.”