Multiple choice

The length of a simple astronomical telescope is

  1. the difference of the focal length of the two lenses

  2. half the sum of focal lengths

  3. the sum of the focal lengths

  4. product of the focal lengths
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A simple astronomical telescope's tube length equals the sum of the objective lens focal length and the eyepiece focal length. This is because the objective forms an image at its focal plane, and the eyepiece is positioned so its focal point coincides with this image plane.

Keep practicing — related questions