The near point of a person suffering from hypermetropia is at 50 cm from
his eye. What is the nature and power of the lens needed to correct this
defect ?
Answers
Answered by
5
Nature of lens is convex lens
power of lens that is needed to correct this defect is 1/50D(IN M) or 2D(IN CM)
power of lens that is needed to correct this defect is 1/50D(IN M) or 2D(IN CM)
Answered by
6
Given :
u=least distant of distinct vision= - 25cm
v= - 50cm
f=?
by lens formula :
1/f=1/v-1/u
1/f=-1/50+1/25
= -1+2/50
1/f=1/50
f=50cm
P=100/f (in cm)
P=100/50
P=+ 2D
Hence P=+2D and f=50cm .
As the focal length is positive so it is convex lens
u=least distant of distinct vision= - 25cm
v= - 50cm
f=?
by lens formula :
1/f=1/v-1/u
1/f=-1/50+1/25
= -1+2/50
1/f=1/50
f=50cm
P=100/f (in cm)
P=100/50
P=+ 2D
Hence P=+2D and f=50cm .
As the focal length is positive so it is convex lens
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