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प्रश्न
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
उत्तर
Adaptation is the ability to adjust vision in bright and dark areas. When we enter a dark room from bright light, the rhodopsin pigment broken down in bright light is regenerated. It dilates the pupil and allows more light to enter the eyes. This is called dark adaptation. On the other hand, if we enter bright area from a dark room, the rhodopsin pigment is bleached. This constricts the pupil and reduces the light entering the eyes. This is called 'light adaptation'
Accommodation is the process of focusing the eye at different distances. This is mainly brought about by a change in the curvature of the lens. When the ciliary muscles contract, the lens becomes thicker and we are able to focus a nearby object. On the other hand when the ciliary muscles relax, the lens remains stretched i.e. the normal condition and we are able to focus on distant object.
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संबंधित प्रश्न
What is the far point and near point of the human eye with normal vision?
What is the other name for
myopia
What is the scientific name of
short-sightedness
Name any two defects of vision which can be corrected by using spectacles.
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
Name the type of defect he is suffering from.
Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and hot it is corrected by a lens.
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
Name an old age eye defect. What happens in it?
What is meant by optical illusion? Give one example.
You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
A person is unable to see distinctly the objects closer than 1 m. Name the defect of vision he is suffering from. Draw ray diagrams to illustrate the cause of the defect and its correction by suitable lens.
A student cannot see a chart hanging on a wall placed at a distance of 3 m from him. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagrams for the (i) defect of vision and also (ii) for its correction.
Distinguish between the following pair of words:
Myopia and hypermetropia
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Name the parts labeled 1 to 4.
Give Reason:
Why do we see clearly in the central region of the retina?
Give Reason:
Deficiency of vitamin A causes night blindness.
Explain the Term: Hypermetropia
Myopia may arise due to ____________.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
