Problem 5.184

A quartz wedge with refracting angle $\Theta=3.5^{\circ}$ is inserted between two crossed Polaroids. The optical axis of the wedge is parallel to its edge and forms an angle of $45^{\circ}$ with the principal directions of the Polaroids. On transmission of light with wavelength $\lambda=550$ nm through this system, an interference fringe pattern is formed. The width of each fringe is $\Delta x=1.0 \mathrm{~mm}$. Find the difference of refractive indices of quartz for ordinary and extraordinary rays at the wavelength indicated above.