Question

A planet is observed by an astronomical reflecting telescope having an objective of focal length 16 m and an eye - piece of focal length 2 cm.

• A. the distance between the objective and the eye - piece is 16.02 m.
• B. the angular magnification of the planet is 800.
• C. the image of planet is erect.
• D. the objective is larger than eye - piece.

Answer 1

Answer: (A), (B), (D)

the distance between the objective and the eye - piece is 16.02 m.
the angular magnification of the planet is 800.
the objective is larger than eye - piece.

Length of astronomical reflecting= distance between the objective and the eye - piece =L,

$f_o=16m$ and $f_e=2cm=0.02m$

$L=f_o+f_e=16+0.02m=16.02m$

Angular magnification $m=\frac{f_o}{f_e}=\frac{16}{0.02}=800$.

In astronomical reflecting telescope, the image formed is inverted.

The objective is always larger than eye - piece.