The focal length of the objective of a compound microscope is $f_0$ and its distance from the eyepiece is $L$. An object is placed at a distance $u$ from the objective. For proper working of the instrument

(A) $L < u$
(B) $L > u$
(C) $f_0 < L < 2 f_0$
(D) $L > 2 f_0$

Choose the correct answer from the options given below:

(B) and (D) only

The correct answer is Option (2) → (B) and (D) only

For a compound microscope, the tube length $L$ must satisfy two conditions:

1. $L > u$ to ensure the objective forms a real, inverted image inside the tube.

2. $L > 2f_0$ ensures sufficient magnification and proper placement of the eyepiece relative to the intermediate image.

Answer: (B) $L > u$ and (D) $L > 2f_0$