Question

Compare the dispersive powers of two prisms if
one of them deviates the blue and red rays through
10° and 6° respectively and the second prism
through 8° and 4.5º​

Answer 1

Answer:

Lets suppose it is a thin prism.

μ  =  δ/α   + 1

Dispersive power (w) = μb − μr/ μ − 1

μ = μb + μr  / 2

so, w = 2(μb − μr)/μb + μr −2

so ratio of despersive power:

w1 / w2 = 10 / α + 1 − 6/α − 1/8/α + 1 −1 ÷ 8 / α + 1 − 4.5/α − 1 /6.25/α + 1 −1

            = 4/α  / 8/α ÷  3.5/α / 6.25/α

            =   4/ 8 ÷  3.5 /6.25 = 0.8928

Thus these are refractive indices for blue and red light.