Question

In a double slits interference experiment, the separation between the slits is 1.0 mm, the wavelength of light used is $5.0\times {10}^{-7}$ m and the distance of the screen from the slits is 1.0 m (a0 Find the distance of the centre of the first minimum from the centre of the central maximum. (b) how many bright fringes ar formed in one ventimetr width on the screen?

Answer 1

Given that, $d=1mm={10}^{-3}m,\lambda =5\times {10}^{-7}m,D=1m$
So fringe width $=\frac{D\lambda }{d}=0.5mm$
(a) So, distance of center of first minimum from centre fo central maximum
$=\frac{0.5}{2}mm=0.25mm$
(b) No. of fringes $=\frac{10}{0.5}=20$