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In normal adjustment, the length and mag...

In normal adjustment, the length and magnifying power of an astronomical telescope are 80 cm and 15 respectively. What are the focal lengths of the objective and the eyepiece ?

A

75 cm, 5 cm

B

90 cm, 6 cm

C

60 cm, 4 cm

D

105 cm, 7 cm

Text Solution

Verified by Experts

The correct Answer is:
A
`M=(f_(o))/(f_(e)) therefore f_(o)=15f_(e)`
and `f_(o)+f_(e)=15f_(e)+f_(e)=16f_(e)=80`
`therefore f_(e)=5 cm and f_(o) =75 cm`
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