Question

For the astronomical telescope, the focal length of objective lens is $f_o$ and the eye piece lens is $f_e$. Then the tube length of the telescope is _____

• A. $L\ge f_o-f_e$
• B. $L\ge f_o+f_e$
• C. $L<f_o+f_e$
• D. $L\le f_o-f_e$

Answer 1

The correct option is B $L\ge f_o+f_e$

For astronomical telescope
$\left|v_1\right|=f_o$
$\left|u_2\right|\le f_e$
Probable answer would be (c) conceptually correct