High-quality camera lenses are often coated to prevent reflection. A lens has an optical index of refraction of 1.72 and a coating with an optical index of refraction 1.31. For near normal incidence, the minimum thickness of the coating to prevent reflection for wavelength of 5.3×10−7 m is
(1) 0.75μm
(2) 0.2 mm
(3) 0.1μm
(4) 1.75 mm