The Total solution for NCERT class 6-12
Aperson looking at a person wearing a shirt with a pattern comprising verticaland horizontal lines is able to see the vertical lines more distinctly than thehorizontal ones. What is this defect due to? How is such a defect of visioncorrected?
Inthe given case, the person is able to see vertical lines more distinctly thanhorizontal lines. This means that the refracting system (cornea and eye-lens)of the eye is not working in the same way in different planes. This defect iscalled astigmatism. The person’s eye has enough curvature in the verticalplane. However, the curvature in the horizontal plane is insufficient. Hence,sharp images of the vertical lines are formed on the retina, but horizontallines appear blurred. This defect can be corrected by using cylindrical lenses.