Question

Flint glass prism is joined by a crown glass prism to produce dispersion without deviation. The refractive indices of these for mean rays are $1.602$ and $1.500$ respectively. Angle of prism of flint prism is ${10}^o$, then the angle of prism for crown prism will be

• A. ${12}^o{2.4}^{\prime }$
• B. ${12}^o{4}^{\prime }$
• C. ${1.24}^o$
• D. ${12}^o$

Answer 1

The correct option is A ${12}^o{2.4}^{\prime }$

For dispersion without deviation $\frac{A}{A^{\prime }}=\left(\frac{{\mu }_y^{\prime }-1}{{\mu }_y-1}\right)$
$\therefore \frac{A}{10}=\frac{(1.602-1)}{(1.500-1)}=\frac{0.602}{0.500}\Rightarrow A={12}^o{2.4}^{\prime }$