The refractive indices of the crown glass for blue and red light are ${\rm{1}}{\rm{.51}}\,{\rm{ and }}\,{\rm{1}}{\rm{.49}}$ respectively and those of the flint glass area ${\rm{1}}{\rm{.77}}\,{\rm{ and }}\,{\rm{1}}{\rm{.73}}$ respectively. An isosceles prism of angle ${6^0}$ is made of crown glass. A beam of white light is incident at a small angle on this prism. The other flint glass isosceles prism is combined with the crown glass prism such that there is no deviation of the incident light <br> (i) Determine the angle of the flint glass prism <br> (ii) Calculate the net dispersion of the combined system