What is Power of Accomodation of Eye?

The ability of the eye lens to change its focal length is called power of accomadation


This focal length of eyes is changed with the help of cillary muscles as explained below

 

When eyes are looking at distant objects

Cillary muscles are relaxed

These pull the eye ligaments tightly

Due to this, eye lens become streched and become thin

So, focal length increases

 

When eyes are looking at nearby objects

Cillary muscles are contracted

Due to this, eye ligaments are loose

Eye lens become thick and we are able to see nearby objects

So, focal length decreases

Power of Accomodation - of near and far objects - Teachoo.jpg

What is Range of Accomodation reached by Normal Eye?

Human Eye can see objects whose distance is between Infinity and 25 cm from Normal Eye


What is Near and Far Point of Eye?

Farthest Point where eye can see is called Far Point of Eye

It is infinity

 

Nearest Point where eye can see is called Near Point of Eye

It is 25 Cm from eye

 

What Is Cataract?

In old age, crystalline lens of some people become milky and cloudy

This is called cataract

It causes partial or complete loss of vision

It can be avoided with the help of cataract surgery

Eye with Cataract.jpg

Why we have 2 eyes for vision and not one?

It helps us to have wider view

With one eye, a human being can see a horizontal field view of 150 degrees

With 2 eyes, a human being can see a horizontal field view of 180 degrees

Explanation

Since both eyes are separated by a distance of few cm, both eyes see different images

Our brain is able to combine 2 images into one and hence we are able to see image with wider view

Hence, we are able to detect faint or far way objects because of our 2 eyes

 

Also,

It helps us judge distances accurately

Because our eyes are separated by a few centimetres, each eye sees the object from different angles.

So, the brain sees two slightly different image

The brain combines the two images into one, using the extra information to tell us how close or far away things are.

  1. Class 10
  2. Chapter 11 Class 10 - Human Eye and Colourful World

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.