Microscopy and magnification

The idea

Electron microscopes have a much higher magnification and resolution than light microscopes, so they show sub-cellular structures such as ribosomes in detail. Magnification = size of image ÷ size of real object. Small sizes are measured in micrometres (µm): 1 mm = 1000 µm.

1. Convert both sizes to the same unit.
2. Use magnification = image size ÷ real size.
3. Rearrange: real size = image size ÷ magnification.

Watch out Forgetting to convert units: 1 mm = 1000 µm, so a 5 mm image of a 50 µm cell is magnified 100 times, not 0.1 times.