CBSE Class 10 Science 2017 · Paper 31(B)/C · Question 17
A student needs a lens of power D. for correcting his vision.
- (i)Name the defect of vision he is suffering from. Write two causes of this defect.
- (ii)What is the nature and focal length of the correcting lens ?
Answer
Myopia, caused by excessive curvature of the eye lens or elongation of the eyeball; the lens is concave, m.
(i) The student suffers from myopia (near-sightedness). Two causes: excessive curvature of the eye lens, and elongation of the eyeball.
(ii) The correcting lens is a concave (diverging) lens, since its power is negative. Its focal length is m, that is, cm.
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