Question

Monochromatic green light, of wavelength $550nm,$ illuminates two parallel narrow slits $7.70\mu m$ apart. Calculate the angular deviation of the third-order $(m=3)$ bright fringe in radians.

Answer 1

We use the equation with $m=3$ :
$\theta ={\sin }^{-1}\left(\frac{m\lambda }{d}\right)={\sin }^{-1}\left[\frac{2(550\times {10}^{-9}m)}{7.70\times {10}^{-6}m}\right]=0.216rad$