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Organisation of the Organism

Magnification and Size of Specimens

Cambridge IGCSE Biology

Magnification

magnification = image sizeactual size
  • Rearranged for the actual size: actual size = image sizemagnification
  • Measure the image with a ruler in mm.
  • Write a magnification as the × sign and a number, with no unit. Never write a unit after a magnification.
  • Give an actual size with its unit, such as mm. Never write an actual size with the wrong unit.
Method: finding the actual size
  1. Measure the line on the image in mm.
  2. Write actual size = image size ÷ magnification.
  3. Divide the image size by the magnification.
  4. Give the actual size with its unit.

Converting millimetres and micrometres

  • 1 mm = 1000 µm.
  • mm to µm: multiply by 1000.
  • µm to mm: divide by 1000.

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