Question

Wave picture of light has failed to explain
(1) photoelectric effect
(2) interference of light
(3) diffraction of light
(4) polarization of light

• A. photoelectric effect
• B.  interference of light
• C. diffraction of light
• D. polarization of light

Hint:

The photoelectric effect provided strong evidence for the particle nature of light, leading to the development of quantum mechanics.

Answer 1

The Correct Option is A

Step 1: Understanding the Wave and Particle Nature of Light 
The wave theory of light successfully explains several optical phenomena such as:

 - Interference (superposition of waves),
- Diffraction (bending of waves around obstacles), and
- Polarization (orientation of light waves).
However, the wave theory failed to explain the photoelectric effect, which involves the ejection of electrons from a metal surface when exposed to light.
Step 2: Why Wave Theory Fails for the Photoelectric Effect 
According to the wave model:
- Energy is spread out across the wavefront.
- Light of any intensity should eventually eject electrons if given enough time.
However, experimental results show that:
- Electrons are ejected instantaneously, without delay.
- The kinetic energy of emitted electrons depends on the 
frequency, not the intensity of light.
- There exists a threshold frequency below which no electrons are ejected, regardless of intensity.
This led to Einstein's particle theory of light, where light is made up of photons, each carrying discrete packets of energy (\( E = h \nu \)).