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प्रश्न
Write short notes on the following: Retina
उत्तर
Retina
Retina is the innermost layer. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. The receptor cells present in the retina are of two types – rod cells and cone cells.
(i) Rod cells –The rods contain rhodopsin pigment (visual purple), which is highly sensitive to dim light. It is responsible for twilight vision.
(ii) Cone cells –The cones contain iodopsin pigment (visual violet) and are highly sensitive to high intensity light. They are responsible for daylight and colour visions.
The innermost ganglionic cells give rise to optic nerve fibre that forms optic nerve in each eye and is connected with the brain. In this region, the photoreceptor cells are absent. Hence, it is known as the blind spot. At the posterior part, lateral to blind spot, there is a pigmented spot called macula lutea. This spot has a shallow depression at its middle known as fovea. Fovea has only cone cells. They are devoid of rod cells. Hence, it is the place of most distinct vision.
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संबंधित प्रश्न
A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D
State whether these lenses are thicker in the middle or at the edges.
A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads :
Left eye : +2.50 D
Right eye : +2.00 D
Which lens bends the light rays more strongly?
What is the:
near point of a normal human eye?
Give the scientific names of the following parts of the eye:
changes shape to focus a picture on the retina.
Fill in the following blank with suitable word:
The part of eye which alters the size of the pupil is............
What changes take place in the shape of eye-lens:
when the eye is focused on a distant object?
The eyes of a person are focused (i) on a nearby object, and (ii) on a distant object, turn by turn. In which case:
the converging power of eye-lens will be the maximum?
How does the eye adjust itself to deal with light of varying intensity?
Sometimes you remember a vivid picture of a dream you saw. What is the role of your eyes in this experience?
Correct and rewrite the statements by changing the biological term that is underlined for the statement:
The part of the eye which can be donated from a clinically dead person is the Retina.
Choose the correct answer.
In the chemistry of vision, the photosensitive substance is _________________
What is meant by power of accommodation of the eye?
Name the following:
The part of the eye responsible for change in the size of the pupil.
What is the nature of the image that forms on the retina?
Mention, if the following statement is True or False
The least distance of distinct vision for the human eye is 25 cm
State the Location:
Iris
State the Function:
Iris
From where the following nerves arise.
Optic nerve
Where is the following located?
Yellow spot
Name the following:
Two pigments of the sensory cells.
