Question

Q/1

1. One side of a glass slab is silvered as shown in the figure. A ray of light is incident on the other side at an angle of incident 45o. Refractive index of glass is √2. The deflection suffered by the ray when it comes out the stab is.


(1) 90o (2) 180o (3) 120o (4) 45o

Answer 1

see figure,

from Snell's law,

$\mu_1sin45^{\circ}=\mu_2sinr_1$

or, $1\times\frac{1}{\sqrt{2}}=\sqrt{2}sinr_1$

or, $sinr_1=\frac{1}{2}$

or,$r_1=30^{\circ}$

again, from Snell's law in 2nd refraction,

$\mu_2sinr_1=\mu_1sinr_2$

or, $\sqrt{2}sin30^{\circ}=1sinr_2$

or,$\frac{1}{\sqrt{2}}=sinr_2$

or,$r_2=45^{\circ}$

now deflection, $\delta=180^{\circ}-45^{\circ}-(90^{\circ}-r_2)$

=$45^{\circ}+45^{\circ}$

= 90°

hence option (1) is correct choice.