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The magnifying power of a telescope is 9...

The magnifying power of a telescope is `9.` When it is adjusted for parallel rays the distance between the objective and eyepiece is `20cm`. The focal lengths of lenses are

A

10 cm, 10 cm

B

15 cm, 5 cm

C

18 cm, 2 cm

D

11 cm, 9 cm

Text Solution

Verified by Experts

The correct Answer is:
C
`m = (f_(o))/(f_(e)) = 9 `
`and f_(o) + f_(e) = 20 rArr 9f_(e) + f_(e) = 20 rArr f_(e) = 2 cm `.
`f_(0) = 18 ` cm.
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