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.

Options

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

A

Explanation

This dispersive power for crown glass `omega=(n_(v)-v_(r))/(n_(y)-1)`
`=(1.5318-1.5140)/((1.5170-1))=(0.0178)/(0.5170)=0.034`
and for flint glass `omega^(')=(1.6852-1.6434)/((1.6499-1))=0.064`