Why dispersion takes place in glass prism but not in the case of rectangular prism??
Dear Student,
When a light ray passes through a glass slab, it is actually dispersed while bending, but when it passes a parallel surface all of the bending is reversed, as a result the dispersed radiation recombine to form a white light. Only the emergent ray shows lateral displacement with respect to the incident ray.
When the light ray is incident on a prism it dispersed and bent and this effect is not reversed as the opposite face is not parallel to the first surface it encounters. Hence, seven components are separated by the prism and not a rectangular slab.
Regards,