Question

A small angled prism of refractive index $1.4$ is combined with another small angled prism of refractive index $1.6$ to produce dispersion without deviation. If the angle of first prism is $6^{\circ }$, the angle of the second prism is:

• A. $6^{\circ }$
• B. $4^{\circ }$
• C. $2^{\circ }$
• D. $8^{\circ }$

Answer 1

The correct option is B $4^{\circ }$

For no deviation through a prism combination,

$A_1({\mu }_1-1)=A_2({\mu }_2-1)$

$⟹A_2=A_1\frac{{\mu }_1-1}{{\mu }_2-1}=6^{\circ }\frac{1.4-1}{1.6-1}$

$=4^{\circ }$