An astronomical refractive telescope has an objective of focal length `20 m` and an eyepiece of focal length `2 cm`.

Options

A. The length of the telescope tube is `20.02 m`.
B. The magnification is `1000`.
C. The image formed is inverted.
D. An objective of a larger aperture will increase the brightness and reduce chromatic aberration of the image.

Answer

A, B, C

Explanation

Here, `f_0 = 20 m and f_e = 2 cm = 0.02 m`
In normal adjustment, length of telescope tube `L = f_0 + f_e = 20.02 m` ltrgt Magnification `= (f_0)/(f_e) = (20)/(0.02) = 1000`
The image formed is inverted (w.r.t. the object). Choices (a),(b) and ( c) are correct.