Question

The refractive indices of crown prism for violet and red lights are $1.523$ and $1.513$. Dispersive power of prism is

• A. $0.19$
• B. $0.019$
• C. $0.0019$
• D. $19$

Answer 1

The correct option is B $0.019$

Dispersive power, $w=\frac{{\mu }_v-{\mu }_r}{{\mu }_y-1}$

where, ${\mu }_y=\frac{({\mu }_v+{\mu }_r)}{2}$

So, ${\mu }_y=(1.523+1.513)/2=1.518$

Therefore $w=\frac{1.523-1.513}{1.518-1}$

$=0.019$