Question

Why does a glass slab do not give spectrum when white light is incident on it

Answer 1

because In glass slab dipersion does not occurs as both of its sides are parallel to each other..


Hope it helps!!!!

Answer 2

Because glass slab acts as a two prisms placed adjacent to each other . Hence when white light gets incident on it then first prism of a glass slab disperses white light into seven colours and second prism of glass slab unites seven colours again into white light and thus white light goes out of glass slab without dispersing