Two narrow slits 3 mm apart are illuminated with light from a sodium lamp (lamda = 589 nm), and an interference pattern appears on a screen 5 meter from the slits.
1) You place an ultra-thin plate of glass with index of refraction n = 1.5 and thickness .160 mm over both of the slits. What happens central maximum?
2) If you were to place another piece of glass, with index of refraction 1.5, over one of the slits. It has the minimum thickness to create dark destructive interference at the formerly bright central maximum. What is the thickness of this glass?