4
✅ Answers
? Favorite Answer
When light enters the first surface of a rectangular slab there is dispersion because each color is bent (refracted) a different amount. But when the dispersed light leaves the second surface, which is parallel to the first surface, each color is refracted back so the colors recombine to give back white light.
When the dispersed light leaves the second surface of a prism it is not refracted back because the second surface is not parallel to the first surface. Indeed the prism surfaces are angled so the light leaving the second surface is refracted in the same direction as it was at the first surface and this just enhances the dispersion resulting in a visible spectrum of colors.
A slab can be divided into two prisms placed opposite to each other by means of a diagonal.
The dispersion by first prism is cancelled by second prism.
Hence overall no dispersion is observed when light passes through a slab.
Glass Slab
Source(s): https://shrinke.im/a8nb3
It does, but the amount is so small we can’t actually measure that it took place.