Question

The powers of the objective lens and eyepiece of an astronomical telescope are \(2D\) and \(20D\) respectively. Find the length of the telescope in normal adjustment.

• A. \(45\,cm\)
• B. \(50\,cm\)
• C. \(55\,cm\)
• D. \(60\,cm\)

Hint:

For an astronomical telescope in normal adjustment, \[ L=f_o+f_e. \] Always convert power into focal length first using \(f=\frac{1}{P}\).

Answer 1

The Correct Option is C