A typical person\'s eye is 2.5 cm in diameter and has a near point (the closest

Question

A typical person's eye is 2.5 cm in diameter and has a near point (the closest an object can be and still be seen in focus) of 25 cm, and a far point (the farthest an object can be and still be in focus) of infinity.

(a) What is the range of the effective focal lengths of the focusing mechanism (lens plus cornea) of the typical eye?

The range of effective focal lengths for the lens plus cornea system is: _____cm ? f ? ____cm.

(b) Is the equivalent focusing mechanism of the eye a diverging or a converging lens? Justify your answer without using any mathematics, and then see if your answer is consistent with your result in part (a).

Explanation / Answer

Part A)
Apply 1/f = 1/p + 1/q

For the near point

1/f = 1/25 + 1/2.5

f = 2.27 cm

For the far point

1/f = 1/(infinity) + 1/2.5

f = 2.5 cm

Thus the answers are 2.27 to 2.5 cm

Part B)

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