A screen is at a distance D = 80 cm from a diaphragm having two narrow slits S 1 and S 2 which are d = 2 mm apart. The slit Si is covered by a transparent sheet of thickness t 1 = 2.5 m and the slit 62 by another sheet of thickness t 2 = 1.25 m as shown in the figure. Both sheets are made of the same material having a refractive index m = 1.40. Water is filled in space between the diaphragm and the screen. A monochromatic light beam of wavelength = 5000 A is incident normally on the diaphragm. Assuming the intensity of the beam to be uniform and slits of equal width, calculate the ratio of intensity at C to the maximum intensity of interference pattern obtained on the screen, where C is the foot of the perpendicular bisector of S 1 S 2 . [Refractive index of water, ]