Off-Normal Antireflection A thin film of MgF2 (n=1.38) is deposited onto glass (n=1.50) so that its antireflection wavelength is 580nm under normal incidence. What wavelength is minimally reflected when the light is incident instead at 45 degrees? Having the light approach at an angle of incidence θi decreases the relative path difference 2nt by multiplying it by the factor cos(θt), where θt is the angle of refraction. Yes, it really decreases it. Enter the numerical value of wavelength in nm: