Question

In a double slit interference experiment, the separation between the slits is $1\cdot 0mm$, the wavelength of light used is $5\cdot 0\times {10}^{-7}m$ and the distance of the centre of the first minimum from the slitts is $1\cdot 0m$
How many bright fringes are formed in one centimeter width on the screen?

Answer 1

Given that,

The distance between the slits is $d=1mm={10}^{-3}m$

The distance of central maximum, from slit $D=1m$.

The wavelength of the light used is $5\times {10}^{-7}m$

So, fringe with is given as

$\beta =\frac{D\lambda }{d}$

$\frac{1\times 5\times {10}^{-7}}{{10}^{-3}}=0.5mm$.

No. of fringes in 1cm $=\frac{10}{0.5}=20$.