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Question

# The focal lengths of the objective and eye-piece of a telescope are respectively 100 cm and 2 cm. The moon subtends an angle of 0.5∘ at the eye. If it is looked through the telescope, the angle subtended by the moon’s image will be

A
100
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B
50
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C
25
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D
10
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Solution

## The correct option is C 25∘f0=100 cm fe=2 cm Angular magnification of telescope m=θiθo=fofe where θo is the angle subtended by the object at the eye and θi is the angle subtended by the final image at the eye. ⇒−1002=θi0.50 ⇒θi=−250 where the minus sign indicates the direction in which we measure the angle.

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