For the sake of simplicity let's suppose I'm talking about the diffraction of light through one slit. Spoiler Are the distances between any two consecutive fringes (apart from the central maximum) exactly equal? Assuming the wavelength, slit width, and distance between slit and screen do not change, that is. Or is it one of those cases of small angle approximation where the difference is so small it's negligible? Why is the central maximum twice as wide? Also, is the "distance between 2 consecutive fringes" equal to the width of a fringe? When talking about distance between fringes I assume we are talking about the distance between their centres (since there aren't really any gaps between them), which is the distance from crest to crest, which should be the same as the distance from trough to trough, which is the width of a fringe. Am I right? Another question I have is why the image in the spoiler above and many others I have found say that the condition for a minimum is when a⋅sinθ = mλ. Assuming m is an integer value, if one ray of light is offset compared to another by a length equal to a multiple of the wavelength, then surely they're in phase, which means they interfere constructively? That should lead to a maximum, not a minimum. Where have I gone wrong in this thought process?