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प्रश्न
Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and hot it is corrected by a lens.
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उत्तर
Hypermetropia is a defect of vision because of which a person cannot see nearby objects clearly but has normal distant vision. Hypermetropia occurs because the converging power of the eye lens is low and the images of nearby objects are formed behind the retina. As a result, the person cannot see these objects clearly. In certain other cases, hypermetropia is caused because the eye ball is too short. This, too, causes the formation of images behind the retina, as the retina is at a smaller distance from the eye lens. The near point of a hypermetropic eye is located more than 25 centimetres from the eye. The following ray diagram explains the hypermetropic eye and how the defect is corrected by using convex lenses. A convex lens is a converging lens that converges light rays and forms virtual images of nearby objects at the eye's near point. The eye lens then easily focusses the light rays from the near point and forms clear images of the objects on the retina.
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संबंधित प्रश्न
A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him. Name the defect of vision the boy is suffering from. Explain the method of correcting this defect.
Draw ray diagram for the:-
(i) defect of vision and also
(ii) for its correction.
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
Name the defect of vision in a person:
whose far point is less than infinity
What is the other name for
hypermetropia
A man can read the number of a distant bus clearly but he finds difficulty in reading a book.
- From which defect of the eye is he suffering?
- What type of spectacle lens should he use to correct the defect?
Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is a young man
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
Draw a ray diagram to show how Hypermetropia is defect can be corrected using a lens.
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.
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
Give Reason:
Older people require glasses to read and write.
Explain the Term: Hypermetropia
What type of lens is used to correct Hypermetropia?
The diagram given below represents the cross-section of the human eye:
(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?
Choose the Odd One Out:
What are the causes of ‘Myopia’?
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.
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.
A person needs a lens of power –4.5 D for correction of her vision.
- What kind of defect in vision is she suffering from?
- What is the focal length of the corrective lens?
- What is the nature of the corrective lens?
