Optics Question 956
Question: 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:
Options:
A) $ 22\frac{1}{2}{}^\circ $
B) $ 45{}^\circ $
C) $ 30{}^\circ $
D) $ 60{}^\circ $
Show Answer
Answer:
Correct Answer: D
Solution:
[d] If we complete the trapezium as shown it becomes an equilateral triangle
$ \Rightarrow $ $ A=60^{o} $ $ \frac{\sin [ \frac{A+{\delta _{\min }}}{2} ]}{sin\frac{A}{2}}=\mu $ $ \frac{\sin [ \frac{60+{\delta _{\min }}}{2} ]}{\sin \frac{60}{2}}=\sqrt{2} $ $ {\delta _{\min }}=30{}^\circ $
