NCERT Solution for Class 10 Science Chapter 11
The Human Eye and the Colorful World
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-190
Questions No-1
What is meant by power of accommodation of the eye?
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When the ciliary muscles are relaxed, the eye lens becomes thin, the focal length
increases, and the distant objects are clearly visible to the eyes. To see the nearby objects
clearly, the ciliary muscles contract making the eye lens thicker. Thus, the focal length of
the eye lens decreases and the nearby objects become visible to the eyes. Hence, the
human eye lens is able to adjust its focal length to view both distant and nearby objects
on the retina. This ability is called the power of accommodation of the eyes.
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Power of accommodation is the ability of the eye lens to focus near and far objects clearly on the retina by adjusting its focal length. Power of accommodation of the eye is limited. It implies the focal length of the eye lens cannot be reduced beyond certain minimum limit.
The power of accommodation is the ability of the eye to focus on distant as well as nearby objects by changing the focal length of lens.This focal length of eyes is changed with the help of ciliary muscles.
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies.
When the ciliary muscles are relaxed, the eye lens becomes thin, the focal length
increases, and the distant objects are clearly visible to the eyes. To see the nearby objects
clearly, the ciliary muscles contract making the eye lens thicker. Thus, the focal length of the
eye lens decreases and the nearby objects become visible to the eyes. Hence, the human eye lens is able to adjust its focal length to view both distant and nearby objects on the retina.
This ability is called the power of accommodation of the eyes.
The power of the eye by which it can see nearby objects as well as faraway objects by changing its focal length is called its power of accommodation.
The term “power of accommodation” refers to the ability of the eye to adjust its focus to see objects at different distances clearly. This adjustment is achieved through changes in the shape of the eye’s crystalline lens.
The eye has the ability to focus on objects at varying distances by changing the curvature of the lens. When viewing objects up close, the ciliary muscles surrounding the lens contract, causing the lens to become thicker and more convex. This increased curvature allows the eye to focus on nearby objects.
Conversely, when looking at objects in the distance, the ciliary muscles relax, and the lens becomes flatter. This reduction in curvature enables the eye to focus on distant objects.
The power of accommodation is measured in diopters (D), and it represents the ability of the eye to adjust its focus from infinity to a certain distance. The unit of diopter is the reciprocal of the focal length measured in meters.
The power of accommodation tends to decrease with age, a condition known as presbyopia. Presbyopia is a natural aging process that makes it more difficult for the eyes to focus on close objects. This is one of the reasons why many people need reading glasses as they get older.