Q: White light is passed through a prism of angle 5°. If the refractive indices for red and blue colours are 1.641 and 1.659 respectively. Calculate the angle of dispersion between them.
Sol: As for small angle of prism , $\large \delta = (\mu -1)A $
$\large \delta_b = (1.659 -1)5^o = 3.295^o $
and , $\large \delta_r = (1.641 -1)5^o = 3.205^o $
$\large \theta = \delta_b – \delta_r = 3.295^o -3.205^o $