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Question
You are given three lenses of power 0.5 D, 4 D, and 10 D to design a telescope.
1) Which lenses should be used as objective and eyepiece? Justify your answer.
2) Why is the aperture of the objective preferred to be large?
Solution
(1) The lens with the smallest power or largest focal length should be used as the objective i.e lens with power 0.5 D.
The lens with the largest power or smallest focal length should be used as the eye-piece i.e. lens with power 10 D.
(2) The aperture is preferred to be large so that the telescope can collect as much as light coming from the distant object as possible.
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