Shown below in light grey is a thin film. Consider the reflections from the top and bottom surface of the film (colored rays in the figure). Suppose we know that n < n2 The lens shown has radii 18.5 cm and 18.5 cm and is made of a material with index of refraction 1.57. Using the shape of the lens to assign the given radii, calculate the focal length of the lens. Consider the case where 18.5 cm is the left side and 18.5 cm the right side. (What would you get if you reversed the order, ie. flipped the lens so the two sides are switched?) Image size: S M L Max