1. The problem statement, all variables and given/known data A glass (Refractive index 1.33) is coated with a thin film. (Refractive index 1.50) Find the minimum thickness of the film, if the glass is to transmit light of wavelength λ. 2. Relevant equations 3. The attempt at a solution Light reflected from the upper surface of the film will suffer phase difference. That's all I know about this problem. Are we looking for constructive interference or destructive interference?