I've been working on my Physics work when I scanned across a section and noticed something that bothered me. The equation: d sin (thetha) = m (wavelength). d is the separation and m is an interger. However, it said to find the bright fringes of a double slit (Young's Double Slit Experiment), use this equation, and also to use this equation for the principal maxima of a diffraction grating. Is there a difference? Are they just two different fancy names for finding the same thing? Also, there's an equation I have to find: x ~ (wavelength)mL/d x being position, m being an interger, L being distance and d being separation. Is that related to the previous equation?