DETERMINING MICROSCOPE MAGNIFICATION USING FOCAL LENGTHS AND TUBE LENGTH FOR AN OBJECTIVE
The formula for this is:
MAG=L/fo
Where L= tube length,
fo=focal length of objective,
So for a tube length of 160 mm, objective of 25 mm fl, the magnification of a 25 mm objective is:
160/25= 6.4X, so on a 160 tube length microscope, a 25 mm or 1 inch objective gives 64X with a 10X eyepiece.
With a 10 inch tube=254mm,
254/25= about 10 so with this tube length, with a 10X eyepiece, the magnification is about 100X
Determining magnification of an eyepiece:
Mag=250mm/Fe + 1
So with an eyepiece focal length of 25 mm, magnification would be 11X
On modern microscopes, the magnification is usually listed for the eyepiece and the objective directly on these and simply magnifying one by the other gives the total magnification. So a 10X eyepiece with a 20X objective gives a magnification of 200X.
