Question

11.A plate of thickness t made of materials of refractive index U is placed in front of one of the slits in double slit experiment, what should be the minimum thickness t which will make the intensity at the centre of the fringe pattern zero?

Answer 1

$$\begin{gathered} \mathrm{Intensity}\mathrm{at}\mathrm{the}\mathrm{centre}\mathrm{will}\mathrm{be}\mathrm{zero}. \\ \mathrm{If}\mathrm{path}\mathrm{difference}=\frac{\mathrm{\lambda }}{2} \\ \mathrm{or}(\mathrm{\mu }-1)\mathrm{t}=\frac{\mathrm{\lambda }}{2} \\ \mathrm{or}\mathrm{thickness},\mathrm{t}=\frac{\mathrm{\lambda }}{2(\mathrm{\mu }-1)} \end{gathered}$$