INTERFERENCE OF LIGHT/PHYSICS

INTERFERENCE OF LIGHT:

The phenomenon by which intensity is redistributed when two light waves from two coherent sources superpose each other.

*INTERFERENCE OF LIGHT  is an example for the Wave nature of light.

*CONSTRUCTIVE : When the two waves are in phase. 

*DESTRUCTIVE: When the to waves are out of phase.

COHERENT SOURCES: S₁ and S₂

Two sources emit light waves of  same frequency(or wave length) with a zero or constant phase difference between them.

CONDITIONS FOR OBTAINING COHERENT SOURCES:

They must be obtained from a single source

Must give monochromatic light.

Path difference must not be large.

CONSTRUCTIVE INTERFERENCE:

When the two waves are in phase create constructive  interference.(If the crest meets a crest or a trough meets a trough).Amplitude turns to be greater and the intensity becomes maximum.For constructive interference the path difference between  the two waves from the two coherent sources must be an integral multiple of lambda.

DESTRUCTIVE INTERFERENCE:

When the two waves are out of phase (180⁰) create destructive interference.(If a crest meets a trough).Amplitudes of the two waves get subtracted and the intensity becomes minimum.

For destructive interference,the path difference between the two waves from the coherent sources must be an odd multiple of lambda.

INTERFERENCE FRINGES:                                         

In Young’s double slit experiments alternate birght  and dark bands  appear on the observation screen due to superposition of two light waves from two coherent sources.

FRINGE WIDTH :

It is the separation between two successive bright or dark fringes.

TO INCREASE FRINGE WIDTH:

1.By increasing the Distance D

2. Decreasing the distance d

3. Using Higher wavelength Light (Beta)