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A ray of light is incident normally on one of the faces of a prism of apex angle 30^{\circ} and refractive index \sqrt{2}. The angle of deviation of the ray is:

Option: 1

0^{\circ}


Option: 2

12.5^{\circ}


Option: 3

\mathrm{15^{\circ}}


Option: 4

22.5^{\circ}


Answers (1)

best_answer

For normal incidence, \mathrm{i_{1}=0,r_{1}=30^{\circ}}
\mathrm{As, \quad r_1+r_2=A \quad \therefore \quad r_2=A-r_1=30^{\circ}} \\\\ \mathrm{As \mu=\frac{\sin i_2}{\sin r_2}}
\mathrm{\begin{aligned} & \mathrm{\therefore \quad \sin \mathrm{i}_2=\mu \sin \mathrm{r}_2=\sqrt{2} \sin 30^{\circ}=\frac{1}{\sqrt{2}} \quad \therefore \ \ \ \ \ \mathrm{i}_2=45^{\circ}} \\ & \mathrm{\text { Or } \delta=\mathrm{i}_1+\mathrm{i}_2-\mathrm{A}=0+45^{\circ}-30^{\circ}=15^{\circ}} \end{aligned}}

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Suraj Bhandari

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