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
(a) Explain the functions of the following parts of the eye: (i) cornea (ii) iris (iii) pupil (iv) ciliary muscles (v) eye-lens (vi) retina (vi) optic nerve(b) If you walk from a dark room into sunlight and back again into dark room, how would your pupils alter in size? What makes this happen?(c) Explain why, we cannot see our seats first when we enter a darkened cinema hall from bright light but gradually they become visible.
(a) Functions of the parts of the eye:
(i) Cornea: It is the front part of the eye that is made of a transparent substance and is convex in shape. The light coming from objects enters the eye through the cornea.
(ii) Iris: It is a flat, coloured and ring-shaped membrane with a hole in the middle called the pupil. Its function is to regulate and controls the amount of light entering the eye by automatically adjusting the size of the pupil according to the intensity of light.
(iii) Pupil: It is a hole in the middle of the iris which appears black because the light that passes through it, gets absorbed by the retina and is not reflected back. Its function is to control the amount of light entering the eye with the help of the iris so that it can be focused on the retina to begin the process of sight.
(iv) Ciliary muscles: It is a circular muscle that accommodates the eye lens, which means it changes the thickness (focal length) of the eye-lens while focussing, by changing its shape and thereby enable us to see objects that are near or far away.
(v) Eye lens: The eye lens is a convex lens made of transparent, soft, and elastic tissues like a jelly made of proteins, that control the formation of an image on the retina by converging the light rays coming from an object.
(vi) Retina: It is a delicate membrane located at the back part of the eye, behind the eye-lens where the image is formed. It contains a large number of light-sensitive cells called ‘rods’ and ‘cones’ that respond to the intensity of light and colour of objects respectively.
Optic nerve - It is located in the back of the eye, and its main function is to transfer or carry visual information (signal) from the retina of the eye to the visual centers of the brain in the form of impulses.
(b) Initially, in a dark room, the pupil remains large so as to allow a large amount of light into the eye. When we walk from a dark room into the sunlight, we feel glare in our eyes as the pupil remains large. Gradually, it contracts and becomes small so that we are able to see clearly.
Again, on moving back from sunlight into a dark room, we are not able to see the surroundings clearly, because the pupil remains small. Gradually, it expands and becomes large so that we are able to see clearly.
This action of the pupil is controlled by the iris, which automatically adjusts the size of the pupil according to the intensity of light received by the eye.
(c) When we enter a darkened cinema hall from bright light, at first we cannot see our seats clearly but gradually they become visible because in bright light the pupil of our eye remains small due to which very little light enters our eye and we cannot see properly. Gradually, when the pupil of our eye expands, allowing more light to enter the eye, then enables us to find our seats.
63 Views
