A refracting telescope has an objective lens of focal length and an eyepiece of focal length . The telescope is adjusted so that the final image is formed at the near point of a relaxed eye (). (i) Find the angular magnification of the telescope in this relaxed‑eye configuration. (ii) If the telescope is instead adjusted for viewing distant stars (final image at infinity), what would be the angular magnification?
Answer
(i)
(ii)
The correct answer is (i) (ii) — (ii) For a final image at infinity, the standard magnification is .
Step-by-step solution
- (i) For a final image at the near point, angular magnification . Substitute , , : , . Thus .
- (ii) For a final image at infinity, the standard magnification is .
Common mistake: Neglecting the extra factor for near‑point adjustment
Concept tested: Telescope magnification
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