Question

A thin prism having refracting angle $10^{\circ}$ is made of glass of refractive index $1.42$. This prism is combined with another thin prism of glass of refractive index $1.7$. This combination produces dispersion without deviation. The refracting angle of second prism should be :

• A. $6^{\circ}$
• B. $8^{\circ}$
• C. $10^{\circ}$
• D. $4^{\circ}$

Answer 1

Answer: (A)

$6^{\circ}$

Answer 2

$(\mu-1) A+\left(\mu'-1\right) A'=0$
$|(\mu-1) A|=\left|\left(\mu'-1\right) A'\right|$
$(1.42-1) \times 10^{\circ}=(1.7-1) A'$
$4.2=0.7 A'$
$A'=6^{\circ}$