Question

A real image of a distant object is formed by a planoconvex lens on its principal axis. Spherical aberration is

• A. absent
• B. smaller if the curved surface of the lens faces the object
• C. smaller if the plane surface of the lens faces the object
• D. the same whichever side of the lens faces the object

Answer 1

The correct option is B smaller if the curved surface of the lens faces the object

In this case, the total deviation is shared between the two surfaces.


The spherical aberration occuring in the image of the plano - convex lens will be minimum when the curved surface faces the object and the light from the object first falls on the curved surface. It happens because the deviation of the ray, in this case, is distributed between the two surfaces.