Which of the following phenomena does not explain by wave nature of light.
A. reflection
B. diffraction
C. photoelectric effect
D. interference
E. polarization
Choose the most appropriate answer from the options given below:

Solution

Physics sir · 3 steps

Go through the list and ask one thing: does the wave picture explain it, or do you need photons?

1. What waves explain. Reflection, diffraction, interference and polarization all come from how waves travel, bend, overlap and vibrate. The wave theory of light explains every one of them.

   Phenomenon	What it needs	Wave nature explains it?
   A. Reflection	waves bouncing off a surface (Huygens' wavelets)	yes
   B. Diffraction	waves bending around an edge or slit	yes
   C. Photoelectric effect	energy arriving in packets hν, so there is a threshold frequency and no time lag	no, it needs photons
   D. Interference	two waves adding up in phase or out of phase	yes
   E. Polarization	the vibration is transverse	yes

2. Why waves fail. In the wave picture, any frequency should eject electrons if the light is bright enough or shines long enough. Experiments show a threshold frequency, no time lag, and a kinetic energy that depends on frequency, not on intensity. Only photons of energy hν explain this.
3. So. Only C, the photoelectric effect, cannot be explained by the wave nature of light. The answer is (a).

The idea to keep. Effects about light travelling (bending, overlapping, polarizing) are wave effects. Effects about light giving energy to matter (photoelectric effect, Compton effect) need photons.

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