Solving Compound Microscope Lens Length Problem

[premed_love]

Homework Statement

The barrel of a compound microscope is 15.9 cm in length. The specimen will be mounted 1.17 cm from the objective, and the eyepiece has a 5.00 cm focal length. Determine the focal length of the objective lens.

Homework Equations

I am using the mirror equation.

The Attempt at a Solution

1/1.17 cm+1/s'=1/15.9 cm
-1.26 cm
adding 1.26 to 1.17=2.433
1/2.433+1/x=1/1.17 this gives me 2.25 cm

I am so lost. Any guidance would be appreciated.[/B]

 

[BvU]

"I am using the mirror equation" is just as lengthy as actually giving that equation. Why not give it ? What mirror equation ?
Why not use a lens equation ? (You do, I think, but it looks weird).

In your working it is unclear what you are doing. Could you be a bit clearer, use symbols and words ?
It looks as if you think the image from the objective is located at the top end of the barrel.
What is -1.26 cm and why do say you add it , but then subtract it ?I had to search for "mirror" in compound microscope to discover there aren't any (at least not between object and ocular) :)

Decide about whether the eye is accommodated or not. Here they say it is focused at 25 cm.

 

[premed_love]

"I am using the mirror equation" is just as lengthy as actually giving that equation. Why not give it ? What mirror equation ?
Why not use a lens equation ? (You do, I think, but it looks weird).

In your working it is unclear what you are doing. Could you be a bit clearer, use symbols and words ?
It looks as if you think the image from the objective is located at the top end of the barrel.
What is -1.26 cm and why do say you add it , but then subtract it ?I had to search for "mirror" in compound microscope to discover there aren't any (at least not between object and ocular) :)

Thanks I figured it out and I meant lens.

Decide about whether the eye is accommodated or not. Here they say it is focused at 25 cm.