Ingraved on the objective lenses are the magnification numbers, generally they will be 4X, 10X, 40X and 100X. The 100X power is the most difficult to use.

The eyepieces magnify the image 10X lenses. The eyepieces work in combination with the objective lenses to give a magnification of 10 times the magnification of the objective lens in position. The total of the objective lenses time the ocular lens goes from 40X, 100X and 400X. The last objective lens (100X) magnifies to 1000 power. The last objective lens requires a drop of immersion oil to prevent excessive loss of light under this magnification. Generally we will not be using this lens.

Notice that the working distance (A), diameter of the field (B), working distance (C) and thickness of the specimen (D) all decrease with increased magnification.