| An isosceles trapezium of reflecting material of refractive index \[\sqrt{2}\] and dimension of sides being 5 cm, 5 cm, 10 cm and 5 cm. The angle of minimum deviation by this when light is incident from air and emerges in air is: |
 |
A) \[22\frac{1}{2}{}^\circ \]
B) \[\text{45}{}^\circ \]
C) \[\text{3}0{}^\circ \]
D) \[\text{6}0{}^\circ \]
Correct Answer: D
Solution :
| [d] If we complete the trapezium as shown it becomes an equilateral triangle\[\Rightarrow \] \[A={{60}^{o}}\] |
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| \[\frac{\sin \left[ \frac{A+{{\delta }_{\min }}}{2} \right]}{sin\frac{A}{2}}=\mu \] |
| \[\frac{\sin \left[ \frac{60+{{\delta }_{\min }}}{2} \right]}{\sin \frac{60}{2}}=\sqrt{2}\] |
| \[{{\delta }_{\min }}=30{}^\circ \] |
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