Question

A prism causes dispersion of white light while a rectangular block does not. Explain.

Answer 1

a rectangular prism is combination of 2 alternate prism so if 1st prism disperse the light,, other one combine the light.
hence no dispersion is seen.

Answer 2

Q- A prism causes dispersion of white light while a rectangular block does not. Explain.

A-In a prism, the refraction of light takes place at the two slant surfaces. The dispersion of white light occurs at the first surface of prism where its constituent colours ate deviated through different angles. At the second surface, these split colours suffer only refraction and they get further separated.

But in a rectangular glass block, the refraction of light takes place at the two parallel surfaces. At the first surface, although the white light splits into constituent colours on refraction but these split colours on suffering refraction at the second surface emerge out in the form of a parallel beam, which gives an impression of white light.