Question

Four lenses having the focal length of + 15 cm, 20cm, + 150cm, and +250cm respectively are provided to make an astronomical telescope. The focal length of the eyepiece to produce the. largest magnification, should be.

• A. +250 cm
• B. +155 cm
• C. 25 cm
• D. +15 cm

Answer 1

The correct option is D +15 cm

In case of astronomical telescope, magnification $=\frac{f_o}{f_e}$
For maximum magnification, $f_e$ should be least. So, $f_e$ should be 15 cm.