An astronomical telescope has the objective lens and the eyepiece of focal lengths 80cm and 5cm respectively. Find its magnifying power, if the final image is formed at a distance of 50cm from the eyepiece.
A
19.6
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B
17.6
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C
14.4
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D
28.8
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Solution
The correct option is B17.6 Given: fo=80cm fe=5cm ve=−50cm
On using lens formula for eyepiece,
1ve−1ue=1fe
⇒1(−50)−1ue=15
⇒ue=−4.54cm
The general formula for magnifying power of a telescope is,