Question

A near sighted person has a near point of 12 cm and a far point of 40 cm. What power corrective lens is needed for her to have clear distant vision? With this corrective lens in place, what is her new near point?

Answer 1

answer :--

for removal of nearsightedness -- u= infinity , v= -40 cm = 0.4 m

• here we use the concept that for removal of near sightedness -- the human will become elligible to see the object at infinite because noe the used lens will make the image of that object at far point of that human eye . so
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• the concave lens of power 2.5 D ..

now using the above corrective lens the near point will change and given by

• f= -0.4 m , u = -0.12 m
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• so the new near point will = 9.231 cm..............................(nswer)