Problem 5.75

A plane light wave with wavelength \(\lambda=0.70 \mu \mathrm{m}\) falls normally on the base of a biprism made of glass \((n=1.520)\) with refracting angle \(\theta=\) \(=5.0^{\circ} .\) Behind the biprism (Fig. 5.15) there is a plane-parallel plate, with the space between them filled up with benzene \(\left(n^{\prime}=1.500\right)\). Find the width of a fringe on the screen \(S c\) placed behind this system.