The cornea behaves as a thin lens of focal length approximately 1.80 , although

Question

The cornea behaves as a thin lens of focal length approximately 1.80 , although this varies a bit. The material of which it is made has an index of refraction of 1.38, and its front surface is convex, with a radius of curvature of 5.00 .
(Note: The results obtained here are not strictly accurate, because, on one side, the cornea has a fluid with a refractive index different from that of air.)

The radius of the curvature of the back side of the cornea is R=18.6mm

b) Where would the cornea focus the image of an 15.0 -tall object at the near point?(The closest distance at which a typical person can focus on an object (called the near point) is about 25.0 , although this varies considerably with age.)


c)What is the height of the image in part B?

Explanation / Answer

Use the lens makers equation: 1/f = ( n - 1 ) ( 1/R1 - 1/R2 ) They give you f =0.0180 n = 1.38 R1 =0.005 and you have to solve for R2 (notice I expressed f and R1 in meters...) So : 1/0.0180 = ( 1.38 - 1) ( 1/0.005 - 1/R2 ) Or: 55.556 = 0.38 *( 200 - 1/R2 ) Or: 146.2 = 200 -1/R2 or 1/R2 = 200 -146.2 = 53.8 invert both sides R2 = 0.0186 meters or R2= 1.86 cm = 18.6 mm so the front is curved outward with a radius of 5.00mm and the back is also curved outward with a radiusof 18.6 mm

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