A drop of liquid of refractive index 1.58 is placed between a plano-convex lens and a plane glass plate which rests on the lens. The material of the plate and lens are identical, having a refractive index of 1.50. Calculate the diameter of the 5th bright ring (fringe) if the radius of curvature of the lens surface is 2.0 m and light of wavelength 590nm is reflected normally from the system. What effect will be observed when the plate is replaced by another whose material has a refractive index of 1.65?