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प्रश्न
Give Reason:
Deficiency of vitamin A causes night blindness.
उत्तर
Because the visual purple (Rhodopsin) of the rods is not formed in the absence of vitamin A.
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संबंधित प्रश्न
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Name the defect of vision in a person:
whose far point is less than infinity
Which defect of vision can be rectified:
by using a convex lens?
What is the scientific name of
short-sightedness
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
Name the body part with which the terms myopia and hypermetropia are connected.
Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help?
Name the following:
The photosensitive pigment present in the rods of the retina.
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
Given below is a diagram depicting a defect of the human eye. Study the same and answer the question that follow:
Name the defect shown in the diagram.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
Name the problem she is facing.
What is Hypermetropia (far sightedness)?
State the main functions of the following:
Tears
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Give two possible reasons for this defect of the eye in human beings.
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Assertion: Concave mirrors are used as reflectors in torches, vehicle head lights and in search lights.
Reason: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real and inverted.
Complete the following table by observing the given figures:
| Figure → |  |
 |
| Points ↓ | ||
| (a) Name of the defect | ______ | ______ |
| (b) Position of the image | ______ | ______ |
| (c) Lens used to correct the defect | ______ | ______ |
