NCERT Solutions for Class 10 The Human Eye and The Colorful World
Class 10 Science The Human Eye and The Colorful World
CBSE class 10 science : Takshila Learning always takes care to design subject matter in such a way that it is always easy for the Class 10th students to understand the concepts and learn how to attempt the question paper in CBSE Class 10 Science exams. Here, we will discuss ‘The Human eye and the colorful world’ from 10 class science.
Our human body is made up of a different sense organ. The Eye is one of the most important sense organs. But have you ever wondered how do we are able to see?
Moving forward, we will share some important notes on the eye structure, working of the human eye, and its defects. We will also discuss how these are corrected by using various lenses. So, let’s start with the human eye.
The human eye
- The Cornea is the front part of the eye. It is expanded towards the outside and made up of a transparent substance. It is convex in shape and the light which comes to the eye is entered through the cornea.
- Iris is behind the cornea and flat in shape, colored, and usually ring-shaped membrane.
- Pupil of the eye is the hole in the middle of the eye. As there is no reflection of light through the pupil hence it is black in color.
- A transparent, soft, flexible jelly-like material is called eye-lens. The shape can be changed due to the flexibility which focuses light on the retina.
- The eye-lens is held in position by suspensory ligaments. One end is attached to the eye-lens and other to the ciliary muscle.
- The screen on which the image is formed in the eye is called Retina.
- The blind spot is a small area of the retina insensitive to light where the optic nerve leaves the eye.
Working of the Eye
The eye consists of a convex lens called eye-lens and a screen called Retina. The eye-lens forms a real image of the objects on the retina of the eye and we are able to see the objects.
In the eye, a convex lens called eye lens forms a real and inverted image of an object on the light-sensitive screen called retina. The light rays coming from the object enter through the cornea of the eye, pass through the pupil of the eye and fall on the eye-lens. When the image falls on retina these light-sensitive cells get activated and generate electric signals. The retina sends these electric signals to the brain through the optic nerves and gives rise to the sensation of vision.
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The function of Iris and Pupil
The iris controls the amount of light entering the eyes. If the amount of light received by the eyes is large then the iris contracts the pupil and reduces the amount of light entering the eyes.
If the amount of light received by the eye is small the iris expands the pupil so that more light may enter in the eyes.
The adjustment of the size of the pupil takes some time.
Rods and cones
The retina of our eye has a large number of light-sensitive cells. There are two kinds of cells in the retina:
- Rods – the rod-shaped cells present in the retina of an eye, which is sensitive to dim light. Due to their presence only we can see things to some extent in the darkness.
- Cones – the cone-shaped cells present in the retina of an eye, which is sensitive to bright light. Cone cells cause the sensation of the color of objects in our eye.
An eye can focus on the images of the distant objects as well as the nearby objects on its retina by changing the focal length of its lens.
The ability of an eye to focus distant objects as well as the nearby objects on the retina by changing the focal length of its lens is called accommodation.
A normal eye has the power of the accommodation which enables objects as far as infinity and as close as 25 cm to be focused on the retina.
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Range of Vision of a normal human eye
The farthest point from the eye at which an object can be seen clearly is known as the ‘Far point’ of the eye. The nearest point up to which an eye can see an object clearly without any strain is called the “near point”
The minimum distance at which an object must be placed so that a normal eye may see clearly without any strain is called the least distance of distinct vision.
The range of vision of a normal human eye is from infinity to about 25 cm.
In the next article, we will discuss defects of vision and their correction, glass prism, dispersion of light, etc. Keep watching the space for more
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