Question

A ray of light is incident at an angle of incidence $60º$ on the glass slab of refractive index $\sqrt 3.$ After refraction, the light ray emerges out from other parallel faces and lateral shift between incident ray and emergent ray is $4\sqrt 3.$ cm. The thickness of the glass slab is ______ cm.

Answer 1

$1 \times sin \ 60\degree = \sqrt 3 \times sin\ r$
$⇒ r = 30\degree$
∴ $I_1 = 4\sqrt 3 \times 2$
$= 8 \sqrt 3\ cm$
∴ Thickness, $t = l_1 cos\ 30\degree$
$= 8 \sqrt 3 \times \frac {\sqrt 3}{2}$
$= 4 × 3$
$= 12\ cm$

So, the answer is $12\ cm$.