Suppose you are observing the interference pattern formed by a Michelson interferometer in a laboratory and a joking colleague holds a lit match in the light path of one arm of the interferometer. Will this have an effect on the interference pattern

Explanation:

In Michelson interferometer , two light waves from different directions are made to overlap so that fringes are formed on the screen due to interference . In it,  two monochromatic and coherent light are made to overlap which have some path difference or phase difference. They form dark and bright fringes .

Now when a match stick is lit in the path of a wave , the fringes will disappear  and an general illumination will be observed on the screen as the light from the lit match stick will not be coherent . Incoherent light can not form stable fringes.

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