Multiple choice

What is the state called, in which one cannot see both the vertical and horizontal lines simultaneously?

  1. Presbyopia

  2. Cataract

  3. Astigmatism

  4. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. Astigmatism is a state in which one cannot see both the vertical and horizontal lines simultaneously.