3 | P a g e
where, μ o = absolute magnetic permeability and ε o = absolute electrical permittivity of free space.
( vi) It failed to explain the phenomenon of photoelectric effect, Compton effect and Raman effect.
Max Planck’ s Quantum Theory
( i) Light emits from a source in the form of packets of energy called quanta or photon.
( ii) The energy of a photon is E == hv, where h is Planck’ s constant and v is the frequency of light.
( iii) Quantum theory could explain photoelectric effect, Compton effect and Raman effect.( iii) Quantum theory failed to explain interference, diffraction and polarisation of light.
de – Broglie’ s Dual Theory
Light waves have dual nature, wave nature according to Maxwell’ s electromagnetic wave theory and particle nature according to Max-Planck’ s quantum theory.
Two natures of light are like the two faces of a coin. In anyone phenomena only its one nature appears.
Energy of photon = hv = hc / λ where, h = Planck’ s constant 6.6 * 10 < sup-34 J / s
de-Broglie wave equation is λ = h / p = h / mv where h denotes Planck’ s constant.
Superposition of Waves
When two similar waves propagate in a medium simultaneously, then at any point the resultant displacement is equal to the vector sum of displacement produced by individual waves.
y = y 1 + y 2
Interference of Light
When two light waves of similar frequency having a zero or constant phase difference propagate in a medium simultaneously in the same direction, then due to their superposition maximum intensity is obtained at few points and minimum intensity at other few points.
This phenomena of redistribution of energy due to superposition of waves is called interference of light waves.