Interference of Light: The phenomenon of redistribution of energy in a medium due to superimposition of waves from two coherent sources of light is called Interference of Light.
Constructive Interference: At points, where the crest of one wave falls on the crest of the other or a trough of one falls on the trough of the other, the amplitude of the resulting wave becomes maximum. Hence the energy or the intensity of light at such points becomes maximum. This is called Constructive Interference.
Destructive Interference: At some other points where the trough of one falls on the crest of the other or crest of one falls on the trough of the other, the amplitude of the resulting waves becomes minimum. Hence the energy or intensity becomes minimum. This is called Destructive Interference.
Law of conservation of energy is obeyed: It should be clearly understood that in interference of light no light energy is destroyed. The loss of energy at the points of destructive interference appears as the increase of energy at the points of constructive interference.
