In Young’s double slit experiment a transparent sheet of thickness t and refractive index `mu` is placed in front of one of the slits and the central fringe moves away from the central line. It was found that when temperature was raised by` Deltatheta`the central fringe was back on the central line (at C). It is known that temperature coefficient of linear expan- sion of the material of the transparent sheet is`alpha`. A young scientist modeled that the refractive index of the material changes with temperature as `Deltamu"= – gama Deltatheta`. Find `Deltatheta` in terms of other given quantities. D and d are given and have usual meaning.

Answer

`Deltatheta=[(mu-1)/((mu-1)alpha-gamma)]`