Wave Optics - Coherent Light's

Description:

Coherent Source

The source of light, which emit continuous light waves of same wavelength, same frequency and in same phase or having a constant phase difference are called coherent sources. Two coherent lights form a consistent image.

Incoherent Source

Two sources are said to be incoherent if they have different frequency and phase difference is not constant with respect to time. Two incoherent lights form an inconsistent image.

NOTE - No two sources of light in the nature can be coherent because, Combination of frequency in one source cannot be same to the combination to frequency in other.

Coherent light can be created using the following two methods −

Splitting the source of light

To create coherent lights, we place a screen with two small holes in between the light source and the observer, this creates an illusion to the observer that there are two different sources of light which are coherent.

Reflection

To create coherent lights, we can place a mirror through which the light wave gets reflected, this creates two waves - one which directly comes from the source and other which is reflected off the mirror. Hence the observer considers both the waves as different sources which generate coherent lights.