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 $10^{\circ}$, then the angle of prism for crown prism will be

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

Answer 1

Answer: (A)

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^{\circ} 2.4^{\prime}$