a) Explain the formation of Newton's rings with reflected monochromatic light. (10M) Discuss why Newton's rings are in circular. b) In Newton's rings experiment the diameter of the 15th ring was found to be 0.590 (4M) cm and that of the 5th ring 0.336 cm. If the radius of the plano convex lens is 100 cm, calculate the wavelength of the light used. What happens to ring diameter if air film is replaced with liquid of refractive index 1.5?