The magnifying power of a telescope with a tube length of is . What is the focal length of its eyepiece?
Step 1. Given data:
The magnifying power of the telescope .
The length of the tube.
Step 2. Formula used:
where the focal length of the eyepiece lens is , and the focal length of the objective lens is
The total length of the telescope
Step 3. Calculating the focal length of the eyepiece,
And,
Thus the focal length of the eyepiece is
Hence, option A is the correct answer.