Question

The compound mirroscope consists of two convex lenses of 5 cm and 20 cm focal length, then which of them will be object lens and eye piece ?
(A) Object lens with 20 cm focal length and eye piece with 5 cm focal length.
(B) Object lens with 5 cm focal leugth and eye piece with 20 cm focal length.
(C) Both should have 20 cm focal length.
(D) Both should have 5 cm focal length.

Answer 1

answer :- option (B) object lens with 5 cm focal length and eye piece with 20cm focal length.

we know,
$\textbf{for a compound microscope focal length}\\\textbf{of an objective lens is smaller}\\\textbf{than eye piece lens.}$
e.g., $\bf{f_0 < f_e}$

where $\bf{f_0}$ is the focal length of objective lens .
$\bf{f_e}$ is the focal length of eye piece lens.