# Interference of Light Wave

Chapter-10|Wave Optics|NCERT 12th Physics:

Interference of Light Wave:

Interference of light is the phenomenon of redistribution of light energy in a medium on account of superposition of light waves from two coherent sources.

Constructive Interference:

At the points where the resultant intensity of light is maximum, interference is said to be constructive.

Destructive Interference:

At the points where the resultant intensity of light is minimum, the interference it said to be destructive.

Theory of Interference of Waves:

Let the waves from two coherent sources of light be

y₁= a sinωt    and   y₂= b sin(ωt+Ø )     – (I)

Where, a and b are the respective amplitudes of the two waves and Ø is the constant phase angle by which second wave leads the first wave.

According to superposition principle

Intensity:

As we know that intensity

For Constructive Interference:  IR  or    A→Max

For Destructive Interference:  IR   or    A→Min
CosØ →Min= -1

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