Question

Spherical aberration in a thin lens can be reduced by
A. using a monochromatic light
B. usinig a boublet combination
C. using a circular annular mark over the lens
D. increasing the size of the lens

Answer 1

Correct Answer - C
Spherical abberation occurs due to the inability of a lens to converge marginal rays of the same wevelength to the focus, as it converges the paraxial rays. This defect can be removed by blocking marginal rays. This can be done by using a circular annular mask over the lens.