A far sighted person has a near point at 100 cm. What must be the power of the correcting lens?

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Q: 21 (NDA-I/2008)
A far sighted person has a near point at 100 cm. What must be the power of the correcting lens?

question_subject: 

Maths

question_exam: 

NDA-I

stats: 

0,3,13,1,2,10,3

keywords: 

{'sighted person': [0, 0, 1, 0], 'lens': [0, 0, 0, 1], 'near point': [0, 0, 1, 1], 'power': [24, 3, 21, 61]}

A far-sighted person has difficulty seeing objects up close, and their near point is farther away than the average person. To correct their vision, a convex lens is used. The power of a lens is measured in diopters (D), with positive values for convex lenses.

Option 1: -0.8 D - This option represents a concave lens, which cannot correct far-sightedness. Therefore, this option is incorrect.

Option 2: -3.0 D - This option also represents a concave lens, which is not suitable for correcting far-sightedness. Hence, this option is incorrect.

Option 3: +0.8 D - This option represents a convex lens, which can be used to correct far-sightedness. However, the power of +0.8 D may not be sufficient to correct a person with a near point at 100 cm. Hence, this option is incorrect.

Option 4: +3.0 D - This option represents a convex lens with a power of +3.0 D. This strong convex lens would be suitable for a far-sighted person with a near point at 100 cm. Therefore, this option is correct.

In conclusion, the correct answer is Option 4, +3

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