Question

The focal length of a simple lens depends on the color (wavelength) of light passing through it. Why? Is it possible for a lens to have a positive focal length for some colors and negative for others? Explain.

Short answer

NO, it is not possible.

Step-by-step solution

Definition of Focal length

The term focal length may be defined as the distance between the center of mirror and its focus.

Explain reason of question

The refractive index of the glass related to the light beam in the glass.depend on the wavelength so on different angles different color are appears. For n > 1 and one type of lens the sign of focal length is same.

Hence, it is not possible for a lens to have a positive focal length for some colors and negative for others.