“Light is emitted with a central wavelength of 500 nm. First it is analysed with a Michelson Interferometer: starting from uniform illumination, one of the mirrors is displaced 2.5 mm until no new fringes can be distinguished. Then it is analysed with a Young´s Double Slit: it is observed that the intensity of the minima adjacent to a certain maximum is not zero, but 0.05% of the maximum intensity. What is the order of said maximum?” So I don´t really have any idea what to do. I tried to obtain order m by finding the intensity ratio: I_max/I_min =cos^2(δ_max/2)/cos^2(δ_min/2) =0.0005 Where: δ_max/2=πm and δ_min/2=π(m+1/2) But it turns out that m is not an integer, but 0.0071. And when I use the standard order equation for the interferometer, I get: 2∆d/λ=∆m And this gives a change in m of about 10000! Basically I don´t understand the link between the two parts of the question and any help would be appreciated.