Question

A thin film with an index of refraction of 1.71 is used as a non-reflective coating on a glass lens that has an index of refraction of 1.52. What is the smallest non-zero thickness (tmin) of the fim that will produce completely destructive interference for light that has a wavelength of 516 nm in vacuum? Assume the light is traveling in air before encountering the film, and that the light strikes the film at normal incidence. This problem is set up to help you work through the problem using a systematic approach, consistent with the five-step method outlined in the textbook (a) First, what is A, the shift for the wave reflecting from the air-coating interface? App Recommendations Emin O 2tmin (b) You should also think about what happens with the wave that reflects from the coating-glass interface. When you put everything together, and bring in the appropriate interference condition, you should get one of the following equations (or something equivalent to one of these equations). The resulting equation (possibly after simplifying a little) is which of the following? Emin-mvsilm tmin-(m +0.50m min-20m+1Mim (c) Solve the equation to find the minimum non-zero film thickness. 150 nm

Why is the answer to the second question 2t=(m+1) but not 2t=(m+0.5) ???? Please include an explanation! Thx!

Answer 1

ㄧㄇㄈ 2m +)