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.
Answers
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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