Optics 3 Question 24
24. Spherical aberration in a thin lens can be reduced by
(a) using a monochromatic light
(1994, 2M)
(b) using a doublet combination
(c) using a circular annular mark over the lens
(d) increasing the size of the lens
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Answer:
Correct Answer: 24. (c)
Solution:
- Spherical aberration is caused due to spherical nature of lens. Paraxial and marginal rays are focused at different places on the axis of the lens. Therefore, image so formed is blurred. This aberration can be reduced by either stopping paraxial rays or marginal rays, which can be done by using a circular annular mark over the lens.
