In young's double slit experiment , two slits 0.18 mm apart illuminated by a light of wavelength 589.3 nm. Calculate the distance of (i) `5^(th)` bright and (ii) `3^(rd)` dark fringes from the midpoint of the interference pattern obtained on a screen kept 0.6 m away from the slits.

Explanation

Given that `d=0.18xx10^(-3)m`
`lambda=589.3xx10^(-9)m. D=0.5 m`
(i) `n=5, x=(n lambda D)/(d)` for bright fringes.
i.e., `x=(5xx5.893xx10^(-7)xx0.6)/(1.8xx10^(-4))=9.82xx10^(-3) m`
(ii) `n=2` for `3^(rd)` dark fringe
`x=(2n+1)(lambda D)/(d)`
i.e. `x=((2.2+1)5.893xx10^(-7)xx0.6)/(1.8xx10^(-4))=4.91xx10^(-3) m`