Q. Two lenses in contact form an achromatic lens. Their focal lengths are in the ratio 2 : 3. Their dispersive powers must be in ratio of

1366 231 Ray Optics and Optical Instruments Report Error

A

1 : 3

8%

B

2 : 3

42%

C

3 : 2

38%

D

3 : 1

12%

Solution:

$\frac{ω _{1}}{f _{1}} + \frac{ω _{2}}{f _{2}} = 0$