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Human Eye and Colourful World — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceHuman Eye and Colourful World5 Marks
Question
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
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Answer

When a person is unable to clearly see distant objects, he is considered a myopic person. Such a person is suffering from myopia. This happens when image is formed in front of the retina.

When a person is unable to clearly see a nearby object, he is considered a hypermetropic person. Such a person is suffering from hypermetropia. This happen when image is formed behind the retina.

Correction of Myopia: A person suffering from myopia needs to use a concave lens of suitable focal length. The concave lens diverges the rays coming from infinity. After refraction from the concave lens, the rays appear to be coming from the far point of this person’s eye. Due to this, a clear image of distant object is made on the retina of that person. That is how a myopic person is able to clearly see distant objects; with the help of suitable concave lens.

Correction of Hypermetropia: A hypermetropic person needs to use a convex lens of suitable focal length. The convex lens converges the light rays coming from a nearby object. As a result, these light rays appear to be coming from the near point of this person’s eyes. Due to this, a clear image of nearby object is made on the retina of that person. That is how a hypermetropic person is able to clearly see nearby objects; with the help of suitable convex lens.

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