The possible way to restore clear vision of those people whose eyeball has elongated is the use of suitable
The possible way to restore clear vision of those people whose eyeball has elongated is the use of suitable
Options
The correct option is B. A concave lens of suitable power is used to restore clear vision in cases where the eyeball has elongated.
Marking Scheme
- 1Identification of the defect as Myopia caused by eyeball elongation. (0.5 marks)
- 2Selection of concave lens as the correct corrective measure. (0.5 marks)
Hint
Recall which defect is caused by the elongation of the eyeball and which lens is used to diverge light rays to move the image back onto the retina.
Quick Oral Answer
Elongation of the eyeball leads to Myopia. Because the eyeball is too long, the lens focuses light from distant objects in front of the retina. We use a concave lens to diverge the light slightly before it enters the eye, allowing the eye's lens to focus the image correctly on the retina.
Analysis & Explanation
According to the NCERT text, the elongation of the eyeball is a primary cause of Myopia (near-sightedness). In a myopic eye, the image of a distant object is formed in front of the retina rather than on it. To correct this, a concave lens of suitable power is used. The concave lens diverges the incoming light rays so that they can be focused precisely on the retina.
- Option A (Bifocal lens): These are used for people suffering from both myopia and hypermetropia, or for presbyopia.
- Option C & D (Converging/Convex lens): These are used to correct Hypermetropia (far-sightedness), where the eyeball has become too small or the focal length is too long.
Common Mistakes
- 1Confusing eyeball elongation (Myopia) with eyeball shortening (Hypermetropia).
- 2Selecting a convex lens instead of a concave lens for myopia correction.
Interesting Facts
The normal human eyeball has a diameter of approximately .
In Myopia, the far point of the eye is nearer than infinity.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2025?
This question carries 1 mark in the CBSE Class 10 Science 2025 examination.
Which chapter does this question come from in Science?
This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Defects of Vision and Their Correction" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2025 paper?
This is a MCQ question from Section A in the CBSE Class 10 Science 2025 paper.