Hey there, I'm new here mainly because I realized how deficient my ability to think in Physics/Math based scenarios really is, plus if I'm going to stay in Premed I need to pass a Phys 101 course in 1st year. So, my question is this.. The windows in an office tower are coated with a film to minimize reflected light of wavelength 550 nm. If the glass has an index of refraction of 1.52 and the film coating has an index of refraction of 1.25, how thick should the film be applied? If someone could help me through and confirm my thinking on this it would be greatly appreciated. Distance traveled by the ray after reflection = 550 / 2 = 225 nm Distance traveled in film = 2x λ (μ(air) / μ(film)) = λ (1 / 1.25) = 550 / 1.25 Total Distance = 2x + (550 / 1.25) / 2 = 2x + 110 Now to go back in the reflection.. (2x + 110)(μ(film) / μ(air)) = 2x(1.25) + 225 nm These should interfere destructively. (2) - (1) = 2x(1.25) = λ/2 x = (λ / (4 x 1.25) ) = 550 / 5 = 110 nm I just don't know if that is how thick the film should be applied on the glass, I am lost.