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If far point or near point of a person 's eye is given how to calculate Power of lens required for the person?

Asked by Nitin Gupta(Birla Senior Secondary School,Pilani) , on 16/2/10

If far point is given take that as the image distance[v]...and object distance[u] as infinity...& if near pt is giiven take 'u ' as 25cm, thn use the lens formula to find the focal length....also remember 1infinity=0.....after getting the focal length substitute tht value in the formula 1f to get the power of the lens...

~thnx~

Posted by Jilin Rachel Abraham(International Indian School) on 16/2/10

Can you explain me why this is so?

Thumbs up for you and please explain me the reasons of taking infinity and how to choose which is image distance or object distance if near and far point are given?

Posted by Nitin Gupta(Birla Senior Secondary School,Pilani) on 16/2/10

see Nitin....far point of a normal person is infinity rite?yeah we 've learnt tht...so we take tht as 'u ' when far point of a myopic eye is given.....& always choose the given value as the image distance coz tht is the image formed on retina of a myopic/hypermetropic eye....& 'u ' will be 25cm/infinity depending on the question.......

thnks a lot for the thumb up!

Posted by Jilin Rachel Abraham(International Indian School) on 16/2/10