Question

Two lenses having f1:F2=2:3 has combination to make no dispersion.Find the ratio of their dispersive power?a)2:3 b)3:2 c)4:9 d)9:4​

Answer 1

b)3:2

Step-by-step explanation:

The dispersive power is the reciprocal of the focal length:

`P=(1)/(f)`

Given the ratio of focal lengths:

`(f_1)/(f_2) = (2)/(3)\\\\((1)/(P_1))/((1)/(P_2))=(2)/(3)\\\\(P_2)/(P_1)=(2)/(3)\\\\(P_1)/(P_2)=(3)/(2)`

Therefore,

P₁ : P₂ = 3 : 2

Hence, the correct option is:

b)3:2