JEE Main 2013 — Wave Optics Question with Solution

A thin glass plate of thickness is $\frac{2500}{3}\lambda$ ( $\lambda$ is wavelength of light used) and refractive index $\mu =1.5$ is inserted between one of the slits and the screen in Young's double slit experiment. At a point on the screen equidistant from the slits, the ratio of the intensities before and after the introduction of the glass plate is :