Magnification

How this is marked

Learn the formula: magnification = image size / actual size. The number one error is mismatched units, so convert both measurements to the same unit (usually mm or micrometres) before dividing, and remember 1 mm = 1000 micrometres. Magnification has no units and is written as, for example, x100. You may be asked to rearrange the formula to find actual size = image size / magnification, so practise all three versions.

In an exam answer

Calculating magnification: 'The drawing is 50 mm wide and the real cell is 0.05 mm wide, so magnification = image size / actual size = 50 / 0.05 = x1000.'

Full topic guide: Organisation of the organism