question_answer 22)

You are given prism made of crown glassand flint glass with a wide variety of angles. Suggest a combination of prisms which will (a) deviate a pencil of white light withoutmuch dispersion (6) disperse (and displace) apencil of white light without much deviation  

Answer:

(a) Angular dispersion produced by two prisms i.e. crown glass and flint glass shouldbe zero in this case       i.e.because for flint glass prism is more than for crown glass. Thus crown glass prism of larger angle is tobe combined with a smaller angled flint glassprism. (b) For no deviation, In the combination of prisms, flint glassprism of greater and greater angle may betried but in any case still this angle will besmaller than the angle of the crown glassprism.