Question

(i) What is meant by.
(A) Spherical aberration?
(B) Chromatic aberration?
(ii) How can spherical aberration be reduced/minimized? Suggest any one method.

Answer 1

$\left(i\right)$ (A) Spherical Aberration: It is the defect of lens due to which, all the parallel rays passing through the convex lens are not focussed at a single point on the principal axis and hence, the image of a point object formed by the lens is blurred. This is called spherical aberration.
(B) Chromatic Aberration: It is the defect of lens due to which the image of a white object formed by a lens is coloured or blurred. This is called chromatic aberration.
$\left(ii\right)$ Spherical aberration can be minimized by using stops. In this method either paraxial or marginal rays are cut off by putting black paper on the lens so that rent of the rays comes to a point focus.