The Total solution for NCERT class 6-12
You are given prisms madeof crown glass and flint glass with a wide variety of angles. Suggest acombination of prisms which will
(a) deviate a pencil ofwhite light without much dispersion,
(b) disperse (anddisplace) a pencil of white light without much deviation.
(a)Place the two prismsbeside each other. Make sure that their bases are on the opposite sides of theincident white light, with their faces touching each other. When the whitelight is incident on the first prism, it will get dispersed. When thisdispersed light is incident on the second prism, it will recombine and whitelight will emerge from the combination of the two prisms.
(b)Take the system of the two prisms as suggested inanswer (a). Adjust(increase) the angle of the flint-glass-prism so that the deviations due to thecombination of the prisms become equal. This combination will disperse thepencil of white light without much deviation.