A person with a weak eyesight uses spectacles. What type of lens is used in the spectacles if a person is not able to see the nearby objects (due to image formed behind the retina) and when the person is not able to see the far-off objects (due to image formed ahead of retina)? (Hint: Use the property of lenses to converge or diverge the rays of light.)
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If the person is not able to see the neraby objects then he should use the convex lens and if the person is not able to see the far-off objects then he should use concave lens.
• The inability to see the far off objects which is also known as the short sightedness can be treated by the use of the powered concave lens due to the back pushing of the light rays near the retina in order to get a better visualisation by the eyes.
• The inability to nearby objects which is also known as the long sightedness can be treated by the powered convex lens due to the refraction properties of the convex lens which is useful for the long sightedness.
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