LIGHT -POST 9

CLASS 8 CHAPTER 16
Light
Day 9


Dear Learners,

In the previous blog, we have learned about light and reflection of light. Let me help you to recall few important points

1. Dispersion of light.
2. Spectrum of light.
3. Formation of rainbow.


Today, we will be learning about one of most important sense organ that is EYE

Happy Learning!😊

At the end of it, you will be able to:
1. explain the parts of eyes.
2. tell the functions of various parts of eye.
3. draw the diagram of internal parts of the human eyes.

THE HUMAN EYE- WHAT IS INSIDE OUR EYES?

Click on the link to get the idea:


EXPLAINATION

The eye is a most important sense organ. Eyes resembles a camera in many ways. The main parts of the eye are shown in figure of your text book page 258.

Let us study the parts of human eye:

1. CORNEA: It is a transparent spherical membrane in front of the eye. Light enters the eye through cornea.

2. IRIS and PUPIL: Iris is a dark coloured muscular diaphragm which has a smaller circular opening in its middle. The central circular aperture of iris is called pupil. The pupil appears black because no light is reflected from it. The iris regulates the amount of light entering the eye by adjusting the size of the pupil.

https://www.youtube.com/watch?v=c4LM-aTIUWM

Do you know: Eye colors depend on the amount of pigment (melanin) found in the iris.

3. EYES LENS: The eye lens is a convex lens made of a transparent jelly-like material. The eye lens is held in position by cililary muscles. Ciliary muscles help in changing the focal length of the eye lens.

4. Retina: The inside surface of the rear part of the eye ball is called retina. The eye lens focuses the image of the object on the retina. The surface of retina consists of the about 125 million light sensitive receptors called as photo-receptors. When light falls on these receptors they send electrical signals to the brain through optic nerve.


5. RODS and CONES: There are two kinds of light sensitive cells on the retina.
(i) Cone shaped: These cells are sensitive to colour.
(ii) Rod shaped- These cells are sensitive to brightness or darkness or dim light.

6. Blind spot: There are no rods and cones at the point where optic nerve leave the eye ball to go the brain. Sp, if an image is formed is this part of the retina then no signal is sent to the brain. As a result the object is not seen. This part of retina is therefore called the blind spot.

Click on the link for more info about blind spot:

Click on the link for complete information about eyes:

Click on the link for information about working of eye:

Home Assignment

1. Read page no 258 of your text book.
2. Practice the diagram of an eye.




Comments

  1. Ronald Jo JosephMay 6, 2020 at 9:08 AM

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  2. Gurdev SinghMay 6, 2020 at 9:09 AM

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  4. Akshat RauthanMay 6, 2020 at 9:14 AM

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