This is the interference pattern on a viewing screen behind two slits.
(image of 7 bright fringes with black fringes between every pair of bright fringes)
How would the pattern change if the two slits were replaced by 20 slits having the same spacing d between adjacent slits? Would the number of fringes on the screen increase, decrease, or stay the same?
The Attempt at a Solution
The formula above says that for constructive interference, the path-length difference between successive slits needs to be an integer multiple of wavelength (lambda). However, I don't see anything in my book about the number of fringes going up or down with N (the number of slits) on the grating. Any advice?
I know that the fringe spacing increases, the width of each fringe decreases, and the brigntness of each fringe increases, but I don't know about the *number* of fringes and whether it goes up or down.