Question

How will you calculate the focal length of a biconvex lens that is used to correct the defect of Hypermetropia? Explain it mathematically. Please Explain Clearly Friends.​

Answer 1

Answer:

Hypermetopia :- A long sighted eyes can see distant objects clearly but nearer objects are not clear visible .

it means Person who face this defect

see clearly of object placed in infinite .

e.g u = -∞ ( negative sign indicate object placed left side of lens )

use formula,

1/v - 1/( -∞) = 1/f

v = f

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calculation of focal length of lens

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we know, eyes see clearly when object placed minimum = 25 cm

hence , u = -25 cm (negative sign indicate object placed left side of lens )

let D is the nearest sightness for hypermetropia eyes .

e.g v = -D cm

now ,

use lens formula,

1/v - 1/u = 1/f

1/(-D) - 1/( -25 ) = 1/f

1/f = 1/25 - 1/D

=(D - 25)/25D

f = 25D/(D -25 ) cm

let D = 100 cm

then focal length ( f ) = 2500/75 =100/3 cm

Explanation:

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