You are given prisms made of crown glass and flint glass with a wide variety of anlges. Suggest a combination of prisms will
a) deviate a pencil of white light without much dispersion.

Explanation

For no dispersion, angular dispersion produced by two prisms should be zero
i.e. `(mu_(b)-mu)A=(mu_(b)-mu'_(r))A'=0`
As `(mu'_(b)-mu'_(r))` for flint glass is more than that for grown glass, therefore `A'lt A` i.e., flint glass prisms of smaller angle has to be suitably combined with crown glass prism of larger angle.