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Monochromatic lightof wavelenght 600 nm ...

Monochromatic lightof wavelenght 600 nm is used ina Young's double slilt experient. One of the slits is covered by a transparent sheet of thicknes `1.8xx10^-5` m made of a material of refractive index 1.6. How many fringe will shift due to the introduction of the sheet?

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When the light travels through as sheet of thickness t, the optical path travelled is `mut`, where `mu` is the refrctive index. When one of the slits is covered by the shet, air is replaced by the sheet and henc, the optical pasthchange by `(mu-1)t`. One fringe shifts when the optical path changes by one wavelength. Thus, the number of fringes shifted due to the introduction of the sheet is
`((mu-1)t)lamda=((1.6-1)xx1.8xx10^-5m)/(600xx10^-9m)=18`.
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