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

Question

The cornea behaves as a thin lens of focal length approximately 1.80 cm , 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 mm .
(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.)

A) If this focal length is in air, what is the radius of curvature of the back side of the cornea?

B) The closest distance at which a typical person can focus on an object (called the near point) is about 25.0

cm , although this varies considerably with age. Where would the cornea focus the image of an 5.00 mm -tall object at the near point?

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

I've posted this question before, but the answers were incorrect, I figured A is 18.6 and B is 19.4. I need the answer for C with a very clear explanation. Thank you.

Explanation / Answer

given

f = 1.8 cm

n 1.38

R1 = 5 mm = 0.5 cm

R2 = ?

a) using Lens makers equation,

1/f = (n-1)*(1/R1 - 1/R2)

1/1.8 = (1.38 - 1)*(1/0.5 - 1/R2)

==> R2 =1.86 cm

= 18.6 mm

b) u = 25 cm

f = 1.8 cm

v = ?

use, 1/u + 1/v = 1/f

1/v = 1/f - 1/u

1/v = 1/1.8 - 1/25

v = 1.94 cm or 19.4 mm

c) magnification, m = -v/u

= -1.94/25

= -0.0776

image height = m*object height

= -0.0776*5

= -0.388 mm

here negative sign indicates that the image is real.

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