# Under the microscope A modern light microscope

Microscopes are used to study cells. Modern light microscopes can magnify images about 1500 times, while electron microscopes can magnify images about two million times.

## Calculating magnification

The of a biological specimen is calculated using this equation:

$magnification =\frac{measured~size}{actual~size}$

Question

A plant cell in a photograph measures 15 mm across. If the actual size of the cell is 0.015 mm, what is the magnification in the photograph?

$magnification = \frac{measured~size}{actual~size}=\frac{15~mm}{0.015~mm}=\times~1000$ Plant cells seen through a microscope

## Calculating actual size

The actual size of a biological specimen is calculated using this equation:

$actual~size =\frac{measured~size}{magnification}$

Question

The nucleus in a photograph of a cell measures 3 mm across. If the magnification in the photograph is × 500, what is the actual size of the nucleus?

$actual~size = \frac{measured~size}{magnification}= \frac{3~mm}{500}= 0.006~mm$

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