Multiple choice

If the focal length of an astronomical telescope increases, its magnifying power will _____.

  1. increase

  2. decrease

  3. remains the same

  4. cannot be predicted
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For an astronomical telescope in normal adjustment, magnifying power M = fo/fe where fo is the objective focal length and fe is the eyepiece focal length. Increasing the objective focal length increases magnification proportionally, assuming the eyepiece focal length remains constant.

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