Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
The human eye can focus objects at different distances by adjusting the focal length of the eye-lens. This is due to:(a) presbyopia (b) accommodation (c) near-sightedness (d) far-sightedness
(b) accommodation
Explanation
The term "accommodation" refers to the ability of the eye to focus objects situated at different distances on the retina by changing the focal length (or converging power) of its lens.
When the eye is focusing on a nearby object, the eye lens bulges and becomes thicker because, while focusing on a nearby object, the ciliary muscles of the eyes contract, loosening the suspensory ligaments attached to the eye. Since these ligaments become loose, they stop pulling the eye lens, due to which the eye lens bulges under its own elasticity and becomes thick (or more convex) so as to increase its converging power. Since the converging power gets increased, the thick eye lens can converge the diverging light rays coming from the nearby object to form an image on the retina.
When the eye is focusing on a distant object, the eye lens gets stretched and becomes thinner because, while focusing on a distant object, the ciliary muscles of the eyes are fully relaxed pulling the suspensory ligaments attached to the eye lens tightly. Since these ligaments become tight, they pull the eye lens, due to which the eye lens becomes thinner (or less convex) so as to decrease its converging power. Since the converging power gets decreased or small, the thin eye lens is sufficient to converge the parallel light rays coming from a distant object to form an image on the retina.
73 Views
