Question

In refraction through a glass slab with parallel faces, incident ray and emergent ray are parallel. Type 1 for true and 0 for false.

Answer 1

Using Snell’s law or law of refraction, we can predict the amount of bending. It is used to understand the relation between angle of incidence and refraction.

The extent of bending of the ray of light at the opposite parallel faces (air-glass interface) and (glass-air interface) of the rectangular glass slab is equal and opposite. This is why the ray emerges parallel to the incident ray.

We can also prove this geometrically, because $\angle 2$ and $\angle 3$ are alternate interior angles.

So, $\angle 2=\angle 3$

By Snell's law at first surface

$n_{glass}=\frac{sin1}{sin2}$

If light light was incident at second surface, then the path of light would be still the same.

So by Snell's law at second surface

$n_{glass}=\frac{sin4}{sin3}$

$\because \angle 2=\angle 3⟹\angle 1=\angle 4$

Therefore, incident and emergent rays are parallel.