Green light of wavelength 5100 A from a narrow slit is incident on a double slit. If the overall separation of 10 fringes on a screen 200 cm away is 2 cm find the separation between the slits.

Explanation

`lambda = 5100 Å = 5100 xx 10^(-10)m`
Width of 10 fringes = 2cm
Fringe width = `2/10 = 1/5 = 0.2 cm = 0.002 m`
`D = 200 cm = 200 xx 10^(-2) m`
`d = (lambda D)/(beta) = (5100 xx 10^(-10) xx 200 xx 10^(-2))/(0.002)`
`= 51 xx 10^(-5) m`.