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The magnifying power of a telescope with tube length 60 cm is 5. What is the focal length of its eye piece ?

1. 40 cm
2. 30 cm
3. 20 cm
4. 10 cm

Correct answer: 10 cm

Solution

The magnifying power of a telescope is given by the ratio of the focal lengths of the objective lens to the eyepiece. Given the tube length and magnifying power, we can derive that the focal length of the eyepiece must be 10 cm to achieve the specified magnification.

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