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Dr. Manishika Jain explains NCERT Class 8 Science Chapter 16: Light Part 2
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sclera is the tough, white outer coating. The front part of the sclera is clear and allows light to enter the eye. This part is called the cornea.
conjunctiva is a thin epithelium, which lines the inside of the eyelids and front of sclera – continuous with cornea epithelium
Eye contains a clear liquid whose outward pressure on the sclera keeps the spherical shape of the eyeball. The liquid behind the lens is jelly-like and called vitreous humour. The aqueous humour in front of the lens is watery.
Lens is transparent and held by suspensory ligament – transparent, flexible and can change shape – refracts light to focus it onto the retina. Behind the pupil of the eye is a lens which is thicker in the centre
In front of the lens is a disc of tissue called the iris – color of eye and control size of pupil
The iris controls how much light enters the pupil, which is a hole in the centre of the iris. The pupil lets in light to the rest of the eye. Pupil pigment is choroid (black pigment which absorbs all light). Pupil size controlled by iris.
The choroid layer, which contains many blood vessels, lies between the retina and the sclera. In the front of the eyeball, it forms the iris and the ciliary body. The ciliary body produces aqueous humour.
retina a light-sensitive layer made up of rods, which detect light of low intensity, and cones, which detect different colours
optic nerve transmits electrical impulses from the retina to the brain
The part of the retina lying directly in front of the optic nerve contains no light sensitive cells. This region is called the blind spot.
Tear glands under the top eyelid produce tear fluid. This is a dilute solution of sodium chloride and sodium hydrogencarbonate. The fluid is spread over the eye surface by the blinking of the eyelids, keeping the surface moist and washing away any dust particles or foreign bodies. Tear fluid also contains an enzyme, lysozyme, which attacks bacteria.
Fovea: In the eye, a tiny pit located in the macula of the retina that provides the clearest vision of all. Only in the fovea are the layers of the retina spread aside to let light fall directly on the cones, the cells that give the sharpest image.
0:00 NCERT Class 8 Science Chapter 16: Light Part 2
0:48 Structure of Eye
7:12 Kind of Vision
7:57 Tear Gland
10:31 Parrot and Cage Experiment
11:41 Issues Related to Vision
13:41 Animal Eyes
15:13 Visually Impaired
15:39 Aids for Visually Impaired
#science #light #eye #structureofeye #kindofvision #teargland #parrot #cageexperiment #issuesrelatedtovision #animaleyes #visuallyimpaired #aidsforvisuallyimpaired #examrace
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