Could anyone explain why it is that as more slits are added the fringes appear sharper?
As a random shot, i would guess its because there is more superposition on the locations that should have constructive superposition, and theres more destructive interference in the positions that shouldnt have light, resulting in a sharper frindge.
This is my guess though
This is pretty much on the mark, even if it is a little hand-wavey - essentially having more slits introduces more constraints when it comes to meeting conditions for constructive interference. This results in thinner fringes because at some small distance away from an interference maxima, there are more destructively-interfering contributions the more slits you have.
Separate names with a comma.