Question

If the refractive indices of crown glass for red, yellow and violet colours are $1,5140,1.5170$ and $1.5318$ respectively and for flint glass these are $1.6434,1.6499$ and $1.6852$ respectively. then the dispersive powers for crown and flint glass are respectively.

• A. $0.034$ and $0.064$
• B. $0.064$ and $0.034$
• C. $1.00$ and $0.064$
• D. $0.034$ and $1.0$

Answer 1

The correct option is A $0.034$ and $0.064$

The dispersive power for crown glass $\omega =\frac{n_v-n_r}{n_y-1}$
$=\frac{1.5318-1.5140}{(1.5170-1)}=\frac{0.0178}{0.5170}=0.034$
and for flint glass ${\omega }^{\prime }=\frac{1.6852-1.6434}{(1.6499-1)}=0.064$