Interference of Light
The superposition of two or more light waves and redistribution of their energies is called interference.
Sources used should be coherent to observe interference phenomenon. Coherent waves are light waves with same frequency, which maintain the same phase or constant phase difference over a distance and time.
Superposition of two coherent waves-Constructive and Destructive Interference.
When two waves are in phase, the amplitude of the resultant wave is equal to the sum of amplitudes of the two waves. The interference produced at these points is known as constructive interference leading to bright band.
When two waves are in opposite phase, amplitude of the resultant wave is equal to zero. The interference produced at these points is known as destructive interference leading to dark band.
If the path difference between two waves is equal to nλ, it results in constructive interference.
If the path difference between two waves is equal to (2n+1) λ/2, it results in destructive interference.
The regions of brightness and darkness are also known as regions of maxima and minima.