Consider the following statements about a microscope and a telescope :
- Both the eyepiece and the objective of a microscope are convex lenses.
- The focal length of the objective of a telescope is larger than the focal length of its eyepiece.
- The magnification of a telescope increases with the increase in focal length of its objective.
- The magnification of a microscope increases with the increase in focal length of its objective.
Which of the statements given above are correct?
1 and 3 only
1 and 4
2, 3 and 4
1, 2 and 3
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2018
2. The focal length of the objective of a telescope is larger than the focal length of its eyepiece: Correct for a refracting telescope, this arrangement helps achieve significant angular magnification.
3. The magnification of a telescope increases with the increase in focal length of its objective: Correct. For a refracting telescope, angular magnification is approximately the ratio of the objective’s focal length to the eyepiece’s focal length (M ≈ f_objective / f_eyepiece). Increasing f_objective increases magnification.
4. The magnification of a microscope increases with the increase in focal length of its objective: Incorrect. For a compound microscope, the magnification produced by the objective is inversely proportional to its focal length (Magnification_objective ≈ L/f_objective, where L is the distance between lenses). Therefore, increasing the focal length of the objective decreases the magnification.