Two slits 0.125 mm aprt are illuinated by igth of wavelength `4500 ^@A`.The screen is one metre way from the plane of the slits.Find the separation between the second bright fringes on both sides of the central maximum.

Explanation

`d=0.125 mm = 0.125 xx 10^(-3) m`
D = 1 m
`lambda = 4500 A = 4500 xx 10^(-10) m`
Distance of 2nd bright fringe from centrol maxima `= y = 2lambdaDd`
`y_(2) = (2 xx 4500 xx 10^(-10) xx 1)/(0.125 xx 10^(-3))`
`y_(2) = (90 xx 10^(-8))/(0.125 xx 10^(-3))`
`y_(2) = 7.2 xx 10^(-3) m = 7.2 mm`
Separation between 2nd bright fringes on both sides of central maxima = `2y_(2)`
`= 2 xx 7.2 = 14.4 mm`