I need to calculate the magnification, m of an objective lens, so I can then x it by the eyepiece value for M to get the total magnification.

Question

I need v/u (v is dist from lens to image; u is dist of object to lens)

I'm using 1/f = 1/v+1/u rearranged for 1/v.

That's: 1/v = 1/f - 1/u. I think?

The object is 26mm away from the lens; the focal length is 25mm.

I keep getting v = 650mm

Any ideas where i'm going wrong please?

Thanks.

Answer 1

The procedurre you need to follow for the total magnification of a compound microscope, which is what you are talking about, is described here:
http://library.thinkquest.org/C003776/ingles/print/microscope.htm

You need to have a specified "barrel length" for the microscope (which is the separation of the lenses) in order to calculate objective magnification. The objective lens forms an intermediate image in front of the eyepiece, and the eyepiece forms an image of the intermediate image 25 cm away.

Answer 2

Thanks drwls, for that. However, the question acually asks me 2 things: the total M; and to find the length of the microscope! The questioner clearly thinks I have enough info to go on from what I've given above.

Charlie