1. The problem statement, all variables and given/known data What is the minimum thickness of coating which should be placed on a lens in order to minimize reflection of 661 nm light? The index of refraction of the coating material is 1.40 and the index of the glass is 1.65. Hint: You must take into account the 180 degree phase-jump on reflection of light from a medium with a lower index of refraction to a medium of higher index of refraction. Also remember that the wavelength of light changes in a medium. The antireflective coating should be half of the minimum length you determine is necessary for destructive interference to occur. 2. Relevant equations Dsin(theta)=m*lambda 3. The attempt at a solution I don't know how to approach this problem. I have read http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/antiref.html#c3 but I don't see it. Can anyone help me?