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:
Answer & explanation
Correct answer: option 2
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) $L > 2f_0$