question_answer

A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed on other side of the lens at a distance of 0.20 m, 0.205 m and 0.214 m respectively. The dispersive power of the material of the lens will be                                                                 [MP PMT 1991]

A)            619/1000                                

B)            9/200

C)            14/205                                    

D)            5/214

Correct Answer: C

Solution :

                   For a lens Þ = .