Question

In a double-slit experiment the angular width of a fringe is found to be ${0.2}^o$ on a screen placed $1m$ away. The wavelength of light used is $600nm$. What will be the angular width of the fringe is the entire experimental apparatus is immersed in water? Take refractive index of water to be $\frac{4}{3}$.

Answer 1

Distance of screen from slits $D=1m$

${\lambda }_1=600nm$

Angular width of fringe in air, ${\theta }_1={0.2}^0$

Angular width of fringe in air, ${\theta }_2$

$\mu =4/3$

Refractive index is related to angular width by,

$\mu =\frac{{\theta }_1}{{\theta }_2}\Rightarrow {\theta }_2={0.15}^o$