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Question
The focal length of a normal eye-lens is about
Options
1 mm
2 cm
25 cm
1m
Solution
2 cm
Given:
Near point of the human eye, u = -25 cm
Distance between the retina and the eye lens, v = 2 cm (approximately)
Thus, we have the focal length, f.
`1/f=1/v-1/u`
`=>1/f ≅1/2 - 1/-25`
`=>1/f ≅27/50`
⇒ f ≅ 2 cm
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