A uniform film of TiO2, 1036 nm thick and having index of refraction 2.62, is spread uniformly over the surface of crown glass of refractive index 1.52. Light of wavelength 515 nm falls at normal incidence onto the film from air. You want to increase the thickness of this film so that the reflected light cancels.
What is the minimum thickness of TiO2 that you must add so the reflected light cancels as desired?
Am i using the wrong formulas? The examples in my book seem to solve these kind of exercises easily... How should i solve this exercise?
The Attempt at a Solution
I have used the formula for destructive reflection from thin film, half-cycle phase shift (2t = mλ with λ = λair/nfilm). However, it is not correct. I have also tried to use the formula for destructive reflection from thin film, no relative phase shift ((2t = m + 1/2)λ), which also did not work. I have mainly used m = 1 because i read somewhere that it is 1 when calculating the minimum thickness.