Question

Why is emergent ray parallel to the incident ray, after the refraction of Incident ray through a glass slab?(All India - 2012)

Answer 1

Answer:

because opposite sides are parallel

Answer 2

Incident rays and emergent rays are parallel to each other due to equal angle of incidence as well as emergence.

When a light passes through rectangular glass slab, it refracts.

Since medium changes and light moves from rarer to denser medium, it deviates towards the normal. The light follows straight path now.

Further, at the end of glass slab, again light changes medium by moving from denser to rarer medium.

This time light deviates away from the normal. Hence, both the rays are parallel to each other.

Angle of incidence is related to angle of emergence by Snell's law.

This law states that, "ratio of the sine of the angle of refraction and the sine of the angle of incidence is always constant and equivalent to the ratio of phase velocities of the two mediums it is passing through."