# Homework Help: Biology Lab Microscope

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1. Jul 21, 2011

### rmusial91

1. The problem statement, all variables and given/known data
To examine a particular blood sample in biology lab, a student uses a compound microscope set to have a magnification of -4530. The objective and eyepiece are both attached to a tube which is 18 cm in length and the eyepiece has a focal length of 2.62 cm. The near point of the person using the microscope is 24 and you can assume she can view the image produced with a fully relaxed eye.

a) What is the focal length of the objective?

b) What is the distance between the blood sample and the objective lens?

2. Relevant equations
Mobjective = -di/do = - di/ fobjective

Meyepiece = N/feyepiece

Mtotal = Mobjective*Meyepiece

3. The attempt at a solution

i tried using these equations...but they didnt work out for me.. unless im using the wrong equation... i got them equation from compound microscope section of a book

2. Jul 22, 2011

### robodobo33

The equations you have are right; you just have to do some substitution. Starting with your most general/biggest one, Mtotal = Mobjective*Meyepiece, sub in the equations that you have for the Mobjective and Meyepiece. Then, plug in the values given by the problem. You will also need to remember that L(length) = fobjective + feyepiece where the f=focal length. Hope this helps! :)