A refracting telescope consists of an objective lens of focal length $120,\mathrm{cm}$ and an eyepiece of focal length $10,\mathrm{cm}$. The telescope is adjusted so that the final image is at infinity (relaxed eye). What is its angular magnification?

Step-by-step solution

1. Recall that for a telescope used with a relaxed eye and the final image at infinity, $M=\frac{f_o}{f_e}$.
2. Insert the given values: $M=\frac{120}{10}=12$.
3. Thus the angular magnification is 12.

Concept tested: Telescope angular magnification relaxed eye

Published 10 October 2026 · How this solution was prepared and checked