A small-angle prism of glass produces angular deviations dv and dr for violet and red light respectively.
a. (i) Show that the angular separation Δ between the two colours is directly proportional to the apex angle A of the prism and write the proportionality constant in terms of suitable refractive indices.
b. (ii) A prism made of the same glass but having apex angle 4.0∘ is substituted for the original one whose apex angle was 6.0∘. Calculate the ratio of the new angular separation to the original value.
c. (iii) What apex angle should the second prism have so that it produces the same angular separation as the first prism? Show your working clearly.