In Young's double slit experiment, the slits are 2mm apart and are illuminated by photons of two wavelengths At what minimum distance from the common central bright fringe on the screen 2m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

​A silicon monoxide ($$n$$​ = 1.45) film of 100 nm thickness is used to coat a glass camera lens ($$n$$​ = 1.56). What wavelength of light in the visible region will be most efficiently transmitted by this system?​

In a single slit diffraction experiment, light of wavelength 600 nm is used and the first minimum is observed at an angle of 30°. The width of the slit is: