Magnification, Size, and Scale Bars
Cells are extremely small but knowing the sizes of objects viewed under the microscope can be really useful.
For example, a plant scientist might want to compare the relative sizes of pollen grains from plants in the
same genus to identify to help identify different species.
With a compound microscope, the magnification is the product of both lenses, so if microscope has a 10x
eyepiece and an 40x objective, the total magnification is 400x.
Magnification is defined as the ratio of the size of the image to the size of the object.
The relationship between these three values can be
shown using the equation triangle to the right,
which offers a quick way of rearranging the values
in order to derive related formulas.
We use micrometers for specimen size under the microscope. The conversion is:
1mm = 1000 μm (micrometers)
Complete the following Chart:
Actual Specimen Size
Image (Drawing) Size
Magnification
0.5 mm
2 cm
200 m
1 cm
40 m
2 cm
100 m
200X
5 cm
100X
4 cm
50X
100m
10mm
4mm
3X
10cm
25X
Magnification = Image size
Actual size
Image
Size
Magnification
Actual
Size
