Light is a form of energy. It ex-bits many properties. Those are Reflection, Refraction, Interference, diffraction, polarisation etc., In those Interference, which shows clearly the conservation of energy.
Definition of Interference:
When two light waves superimpose then alternative bright and dark fringes are formed in the region of superimpose.
or
The modification of intensity in the region of superimpose.
For better understanding of interference we should know the principle of superposition and phenomenon of coherence.
Principle of Superposition:
The resultant displacement of a particle of the medium acted upon by two or more waves (mixing of waves of same frequency ) simultaneously is the algebraic sum of the displacements of the same particle due to individual waves, in the absence of the others.
Resultant displacement may increase or decrease depending upon the path or phase difference of the waves mixing at that region.
According two the superposition of the waves, interference two types.
1) Constructive interference
2) Destructive interference.