Multiple Slits

When light from a laser travels through very narrow, closely spaced slits and recombines on a screen, the intensity on the screen will depend on the interference between rays passing through the slits. It can be shown that if d is the distance between adjacent slits, then the position of the n^th bright spot (n^th order maximum) is given by:

where y_n is the distance from centre (n=0) to the centre of the n^th order. This equation applies two or more slits with the intensity becoming sharper with more slits.

Single Slit and Obstacles

For a single slit (or an obstacle), a similar formula applies but to intensity minima (center of dark areas) and d now refers to the slit width.