CBSE 2022 · Region 5 · Set 3 · Q10 · 3 marks
A ray of light passes through a prism of refractive index $\displaystyle \sqrt{2}$ as shown in the figure. Find :
(i)The angle of incidence $\displaystyle \left(\angle \mathrm{r}_{2}\right)$ at face AC.(ii)The angle of minimum deviation for this prism.
A ray of light passes through a prism of refractive index $\displaystyle \sqrt{2}$ as shown in the figure. Find :
(i)
The angle of incidence $\displaystyle \left(\angle \mathrm{r}_{2}\right)$ at face AC.
(ii)
The angle of minimum deviation for this prism.
Marking-scheme solution
(i)
As the emergent ray grazes along the side AC, therefore
$$\frac{1}{\sqrt{2}}=\frac{\sin r_{$\displaystyle 2$}}{\sin $\displaystyle 90$^{$\displaystyle 0$}}
$$\therefore r_{$\displaystyle 2$}=$\displaystyle 45$^{\circ}
$$(ii) $\displaystyle \mu=\frac{\sin \left(\dfrac{A+\boldsymbol{\delta} m}{2}\right)}{\sin \dfrac{A}{2}}$
$$\sqrt{2}=\frac{\sin \left(\dfrac{$\displaystyle 60$^{$\displaystyle 0$}+\boldsymbol{\delta} m}{$\displaystyle 2$}\right)}{\sin $\displaystyle 30$^{$\displaystyle 0$}}
$$\therefore \delta_{\mathrm{m}}=$\displaystyle 30$^{$\displaystyle 0$}
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.