18.Consider a soap film that is the thinnest film that will produce a bright blue light when illuminated with white light.The index of refraction of the soap film is 1.35,and the blue light is monochromatic with wavelength 411nm.Solve the following equations,keeping 3 significant figures for your final answer. aCalculate the thickness of the film if the soap covers a piece of crown grass with index of refraction 1.52. bSuppose the reflections occur instead from a soap film on water with index of refraction 1.33.Determine the thickness of the film on water that will produce the same blue colour of reflected light