Two slits are made 0.1 mm apart and the screen is placed 2 m away. The fringe separation when a light of wavelength 500 nm is used is _______________.
Fill in the blank with the correct answer from the option given below.

​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: