glass slab refraction

Refraction of Light through a Glass Slab

Let us now perform an experiment and find out how light gets refracted when it is incident on a rectangular glass slab.

• Place a rectangular glass slab on a white sheet of paper fixed on a drawing board.

• Trace the boundary ABCD of the glass slab.

• Remove the glass slab. Draw an incident ray IO on AB.

• Draw the normal at point of incidence (NN¹ through O)

• Fix two pins P and Q on the incident ray IO.

• Place the glass slab within its boundary ABCD.

• Looking from the other side of the glass slab fix two pins R and S such that your eye and the feet of all the pins are in one straight line.

• Remove the glass slab and the pins. Mark the pin points P₁, P₂, P₃ and P₄.

• Join OO¹.It is the refracted ray.

• Measure are the angle of incidence, angle of refraction and angle of emergence respectively.

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• Extend O¹E backwards. The emergent ray is parallel to the incident ray.

Refraction through a Glass Slab
The above experiment shows that

• When a ray light is passing from air to glass, that is, from a rarer medium to a denser medium, the refracted ray bends towards the normal drawn at the point of incidence. In this case But when the ray of light is passing from glass to air, that is, from a denser medium to a rarer medium the refracted ray bends away from the normal. In this case

• The emergent ray, O¹E which is nothing but the refracted ray emerging out of the glass slab is parallel to the incident ray. This means that the refracted ray (emergent ray) has been displaced from its original path by a distance XY. This displacement is referred to as lateral displacement.