Question

The distance between the principal focus and optical centre is called ______.

विकल्प

• displacement

• radius of curvature

• focal length

• light year

Answer 1

The distance between the principal focus and optical centre is called focal length.

Explanation:

By definition, the distance from the optical centre of a lens to its principal focus is called the focal length. Radius of curvature is the radius of the sphere of which the lens surface is a part.