(b) Explain how a thin film of refractive index n can be used as an anti-reflective coating on a glass lens with refractive index ng. Give the equations that describe the destructive interference condition for the two main reflected light components. (7 marks) (c) A thin oil slick (n = 1.28) is observed on the surface of water (n = 1.33). When a beam of white light strikes this oil film, only green light is seen in reflection of wavelength 550 nm. From this information, calculate a thickness of the oil film on the water. (5 marks)