Question

White light is used in a YDSE with $D=1m$ and $d=0.9mm$. Light reaching the screen at position $y=1mm$ is passed through a prism and its spectrum is obtained. Find the missing lines in the visible region of this spectrum.

Answer 1

Formulae,

For minima,

$\Delta P=\frac{(2n-1)\lambda }{2}$

$\frac{yd}{D}=\frac{(2n-1)\lambda }{2}$

$900=\frac{(2n-1)\lambda }{2}$

$\lambda =\frac{1800}{2n-1}$

$=\frac{1800}{1},\frac{1800}{3},\frac{1800}{5},\frac{1800}{7}$

of these, $600,350nm$ lie in visible region.