Compound microscope focal length

[Cataklyzm]

Homework Statement

The barrel of a compound microscope is 15 cm in length (distance between lenses). The specimen will be mounted 1.0
cm from the objective, and the eyepiece has a 5.0-cm focal length. Determine the focal length
of the objective lens.
Known: f₂=5cm, L=15cm, d_o1=1cm
Unknown: f₁, d_i1, d_i2, d_o2

Homework Equations

1/di+1/do=1/f

The Attempt at a Solution

A. I drew a diagram: I believe d_i1+d_o2=L
B. I have the equations:
1/d_i1+1=f/f₁
1/d_i2+1/d_o2=1/5
d_i1+d_o2=15

I think there is some relation to distances that I'm not seeing.

 

[Cataklyzm]

Must the intermediate image be formed at the focal point of the eyepiece? I think that could solve my distance dilemma.

 

[rude man]

Must the intermediate image be formed at the focal point of the eyepiece? I think that could solve my distance dilemma.

Yes, and you should be able to explain why (hint: the normal human eye likes plane waves!).