Q34 of 70 Page 11

What is Astigmatism?

Astigmatism is the defect of an eye due to which a person cannot focus on both the horizontal and vertical lines, simultaneously. The reason for this defect is irregularities on the surface of the cornea.

More from this chapter

All 70 →
32 A telescope has an objective of focal length 140.0 cm and an eyepiece of focal length 5.0 cm. Find
(i) the magnification of the telescope for viewing distant objects for normal adjustment
(ii) separation between the objective lens and the eyepiece. 33 A 52-year old near-sighted person wears eye-glass with a power of –5.5 dioptres for distance viewing. His doctor prescribes a correction of +1.5 dioptres in the near-vision section of his bi-focals. This is measured relative to the main part of the lens (i) What is the focal length of his distance-viewing part of the lens? (ii) What is the focal length of the near-vision section of the lens? 35 Explain the angle of prism. 36 What is dispersion?