Ray Optics Question 10
Question 10 - 30 January - Shift 2
A thin prism $P_1$ with an angle $6^{\circ}$ and made of glass of refractive index 1.54 is combined with another prism $P_2$ made from glass of refractive index 1.72 to produce dispersion without average deviation. The angle of prism $P_2$ is :
(1) $6^{\circ}$
(2) $1.3^{\circ}$
(3) $7.8^{\circ}$
(4) $4.5^{\circ}$
Show Answer
Answer: (4)
Solution:
Formula: Refraction Through Prism
$\delta_1=\delta_2$ [for no average deviation]
$\Rightarrow 6^{\circ}(1.54-1)=A(1.72-1)$
$\Rightarrow A=\frac{6^{\circ} \times 0.54}{0.72}$
$ =\frac{18^{\circ}}{4}=4.5^{\circ} $
