Fringes are produced by a Fresnel’s biprism in the focal plane of a reading microscope which is 100cm from the slit. A lens is inserted between the biprism and the microscope gives two images of the slit in two positions. In one case, the two images
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Answer:
A Fresnel Biprism is a thin double prism placed base to base and have very small refracting angle ( 0.5o). This is equivalent to a single prism with one of its angle nearly 179° and other two of 0.5o each.
The interference is observed by the division of wave front. Monochromatic light through a narrow slit S falls on biprism , which divides it into two components. One of these component is refracted from upper portion of biprism and appears to come from S1 where the other one refracted through lower portion and appears to come from S2. Thus S1 and S2 act as two virtual coherent sources formed from the original source. Light waves arising from S1and S2 interfere in the shaded region and interference fringes are formed which can be observed on the screen .
Explanation: