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Find the focal length of contact lenses that would allow a nearsighted person with a 130 cmcm far point to focus on the stars at night.

1 Answer

1 vote

Answer:

130cm

Step-by-step explanation:

The lens equation is expressed as;

1/f = 1/u+1/v where;

f is the focal length of the lens

u is the object distance

v is the image distance

Since the near sighted person wants focus the starts at nigt, the stars at night are the images located that infinity. Hence the image distance v = ∞.

The object distance u = 130cm

Substituting the given parameters in the formula to get the focal length f


(1)/(f) = (1)/(\infty) + (1)/(130) \\\\As \ x \ tends \ to \ \infty, \, (a)/(x) \ tends \ to \ 0 \ where\ 'a' \ is \ a\ constant \\\\} \\\\


(1)/(f) = 0+ (1)/(130)\\\\


(1)/(f) =(1)/(130)\\cross\ multiply\\\\f = 130*1\\\\f = 130cm

Hence the focal length of contact lenses that would allow a nearsighted person with a 130 cm far point to focus on the stars at night is 130cm

User Iamnotsam
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