Which one of the following spherical lenses does not exhibit dispersion? The radii of curvature of the surfaces of the lenses are as given in the diagrams. `

Options

A.
B.
C.
D.

Answer

C

Explanation

`(1)/(f)=(mu-1)((1)/(R_(1))-(1)/(R_(2)))`
For no dispersion,
`d((1)/(f))=0`
or `d(mu-1)((1)/(R_(1))-(1)/(R_(2)))=0`
or ` R_(1)=R_(2)`