Question

dispersion is observed in glass prism but not in glass slab why?

Answer 1

The faces of the prism are not parallel to each other. but in glass slab, the opposite faces of the slab are parallel.

Answer 2

Dispersion occurs when light is passed through a prism. The dispersion is caused due to the the difference in the angle of deviation for different colours.

In the case of a glass slab, the opposite sides are parallel and therefore different colors emerge parallel to each other and are seen simultaneously. Therefore, dispersion doesn’t occur in a glass slab.

In a prism, the dispersion occurring at one face in enhanced by the refraction at the other face, but in a glass slab the dispersion occurring at one face is neutralized by refraction at the other face.

hope it will help u