1. Blue light at 480nm impinges perpendicularly on a pair of very narrow parallel slit apertures separated by 0:15mm. A fringe pattern appears on a screen 2m away. How far (in mm) from the central axis on either side will we find the second-order (m = 2) bright bands?
2. Red plane waves from a ruby laser (lambda= 694.3nm) in air impinge on two parallel slits in an opaque screen. A fringe pattern forms on a distant wall, and we see the fourth bright band 1 degree above the central axis. Calculate the separation between the slits (in mm).
3. Parallel rays of blue light from an argon ion laser (lambda = 487.99nm) are incident on a screen containing two very narrow slits separated by 0:2mm. A fringe pattern appears on a sheet of film held 1m away. How far (in mm) from the central axis is the fourth maximum?