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If the power of lens is -2.5 D, what is the focal length of the lens ?

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If the power of lens is -2.5 D, what is the focal length of the lens ?


1 Answer


Given  , 

power of lens p = -2.5 D 

focal length of lens f = ?/

according to the formula, 

p = 1/f 

f = 1/p 

= 1/1.5 

= 0.66 m 

= 66 cm

Here the lens used is convex lens, so the student is suffering from the long sightedness or hypermetropia. 

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