Question

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

• A. $L<u$
• B. $L>u$
• C. $f_0<L<2f_0$
• D. $L>2f_0$

Answer 1

Answer: (B), (D)

$L>u$
$L>2f_0$

For proper working of the compound microscope, the image $I_1$ must be obtained on the left of the eye lens, otherwise the image $I$ would not be obtained as it is now. For this to happen, the distance between lenses L must be large. Hence $L>u$ and $L>2f_0$