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Two plane mirrors, a source S of light, ...


Two plane mirrors, a source S of light, emitting monochromatic rays of wavelength `lamda` and a screen are arranged as shown in figure. If angle `theta` is very small, calculate fringe width of the interference pattern formed by reflected rays.

Text Solution

Verified by Experts

The correct Answer is:
`(2(a+b)lamda)/(4atheta)`

Distance between two sources `S_(1)` and `S_(2)` `d=2xx2acosthetasintheta=2asin2theta`
Screen distance `D=b+2acos^(2)theta`
`beta=(lamdaD)/(d)=(lamda(b+2acos^(2)theta))/(2asin2theta)=(lamda(b+2a))/(4atheta)`
(if `theta` is very much small)
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