Question

4. With the help of a suitable diagram, explain the meaning of terms: (a) centres of curvature (b) optical centre (c) focus ​

Answer 1

a)The centre of curvature of a lens is defined as the center of the spherical surface from which the lens has been cut. 

b) The Optical centre of the lens is defined as the point which lies on the principal axis through the rays of light passes without any deflection

c) The focus is the point, or plane, at which light rays from infinity converge after passing through a lens. It's also known as focal point.

Hope it helps.