As, the final image in formed at infinity by the eye lens, so the object distance for eye lens is focal length of eye lens. So, ‌‌ue=6‌mm=0.6‌cm The distance between the objective and eye lens is 20.6‌cm. ∴‌‌L=v0+ue‌⇒v0=L−ue ‌=20.6−0.6 ‌=20‌cm Let u be the object distance form objective, then from lens formula for objective. ‌
1
f0
=‌
1
v0
−‌
1
u0
‌⇒‌
1
u0
=−‌
1
f0
+‌
1
v0
=‌
1
20
−‌
1
0.6
‌=−‌
19.4
12
‌ or ‌‌‌u0‌=−‌
12
19.4
=−0.62‌cm. So, the magnification of objective, m‌=‌