Hi, I was wondering if anyone could help with this problem that I am stuck on? 1. The problem statement, all variables and given/known data I need to work out a formula for the irradiance(intensity) as a function of the distance for a LLoyd's mirror interference arrangement. The question suggests considering the similarities with the Young Double Slit experiment. 2. Relevant equations I know that the total irradiance is given by I = I_1 + I_2 + [2 (I_1 I_2)^0.5] cos(δ) I know the total irradiance for the double slit experiment is given by I = 4I_0 cos^2(∏ay/λL) I have found that the answer for the Lloyd's mirror is I = 4I_0 sin^2(∏ay/λL) So it is clearly very similar. 3. The attempt at a solution I have the working out for the Young's set up, and I can follow that, but I can't get it to work for the LLoyd's set up, mainly because I can't find a decent diagram for the angles. Any help or if anybody knows of a decent diagram would be much appreciated.