Interference of light

The best evidence for the wave nature of light is interference phenomenon. This was experimentally demonstrated by Thomas Young in 180, through double slit experiment. Due to interference, we will observe many observations in our day today life, such as multiple colours on soap bubbles as well as on oil film when viewed under sun light. Interference concept is explained on the basis of superposition of wave’s concept. When two light waves superimpose, then the resultant amplitude or intensity in the region of superposition is different than the amplitude of individual waves

  Types of interference:- For the formation of interference pattern, two coherent light sources are required. To get two coherent sources form a single light source, two techniques are used. They are

 1. Division of wave fron
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2. Division of amplitude

Division of wave front The wave front from a single light source is divided into two parts using the phenomenon of reflection, refraction, or diffraction. Young’s double slit experiment is belongs to this class of interference. Division of amplitude The amplitude of a single light beam is divided into two parts by parallel reflection or refraction. Newton’s ring experiment, Michelson’s interferometer is belongs to this class of interference.

  Conditions for interference

1) Two light sources of emitting light waves should be coherent.
 2) Two sources must emit continuous light waves of same wavelengths or frequency.
3) The separation between the two sources should be small.
4) The distance between the two sources and the screen should be large.
5) To view interference fringes, the background should be dark.
6) The amplitude of light waves should be equal or nearly equal.
7) The sources should be narrow.
 8) The sources should be monochromatic