Two slits are made one millimetre apart and the screen is placed one metre away. What is the fringe separation when blue- green light of wavelength 500 nm is used ?

Explanation

`d = 1 mm = 1 xx 10^(-3) m`
`D = 1m`
`lambda = 500 nm = 500 xx 10^(-9) m`
`beta = (lambda D)/(d) = (500 xx 10^(-9) xx 1)/(10^(-3)) = 500 xx 10^(-6) m`.