A person is unable to see the objects beyond 2m clearly. Name the defect of
vision he is suffering from. State two causes due to which this defect may arise.
Draw ray diagrams to show the defect of vision and correction of this defect
using an appropriate lens.
Answers
a) Myopia is also known as near-sightedness. A person with myopia can see nearby objects clearly but cannot see distant objects distinctly. A person with this defect has the far point nearer than infinity. Such a person may see clearly upto a distance of a few metres. In a myopic eye, the image of a distant object is formed in front of the retina and not at the retina itself. This defect may arise due to: (1) excessive curvature of the eye lens, or (2) elongation of the eyeball.
(i) The student is able to see the objects clearly upto 5m, i.e., his far point is 5m. For a myopic eye with the near point as 5m, if any object is kept beyond this distance, the image is not formed on the retina. Instead, the image is formed in front of the retina as shown in the figure. Hence, the student is unable to see distinctly the object places beyond 5m from his eyes.
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5m
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)=
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1 =
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1 = −5m
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1 = −5m1
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1 = −5m1
(ii) This defect can be corrected by using a concave lens of suitable power. A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.(b) Given, focal length (f)=−5mPower(P)= focal length(f)1 = −5m1 =−0.2D
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Answer:
myopia is the defect
when a person can't see the objects beyond the far point is called myopia
reasons for this defect:
- becoz of the big size of eye ball the image is not formed when object is far
- becoz of no accomodation of the lens
to correct this defect concave lens is used
i think this is the answer..........
i hope this helps u
