Question

A planet is observed by an astronomical refracting telescope having an objective of focal length $16\, m$ and an eyepiece of focal length $2\, cm$

• A. The distance between the objective and the eyepiece is 16.02 m
• B. The angular magnification of the planet is -800
• C. The image of the planet is inverted
• D. The objective is larger than the eyepiece

Answer 1

Answer: (A), (D)

Tube length $=f_{o}+f_{e}$
Angular magnification $=\frac{f_{o}}{f_{e}}$
Then, $f_{o}+f_{e}=16+0.02=16.02\,m$
Angular magnification $=\frac{f_{o}}{f_{e}}=-\frac{16}{0.02}=-800$
Objective lens is larger than eyepiece in aperture focal length.