Q. Let the refractive indices of crown glass for red, yellow and violet colours are $1.5140,1.5170$ and $1.5318$ respectively and similarly that for flint glass these are $1.6434,1.6499$ and $1.6852$ , respectively. Then what are the dispersive powers for crown and flint glass, respectively ?
NTA AbhyasNTA Abhyas 2022
Solution:
Dispersive power, $\omega $ is given by :
$\omega =\frac{\mu _{v} - \mu _{r}}{\mu _{y} - 1}$
Substituting it in both the mediums :
$\omega _{1}=\frac{1 . 5318 - 1 . 5140}{1 . 5170 - 1}=0.034$
$\omega _{2}=\frac{1 . 6852 - 1 . 6434}{1 . 6499 - 1}=0.064$
$\omega =\frac{\mu _{v} - \mu _{r}}{\mu _{y} - 1}$
Substituting it in both the mediums :
$\omega _{1}=\frac{1 . 5318 - 1 . 5140}{1 . 5170 - 1}=0.034$
$\omega _{2}=\frac{1 . 6852 - 1 . 6434}{1 . 6499 - 1}=0.064$