CIE A Level Biology复习笔记1.1.2 Magnification Calculations

Magnification Calculations

  • Magnification is how many times bigger the image of a specimen observed is in comparison to the actual (real-life) size of the specimen
  • The magnification (M) of an object can be calculated if both the size of the image (I), and the actual size of the specimen (A), is known

Magnification-EquationAn equation triangle for calculating magnification

Worked Example

An image of an animal cell is 30 mm in size and it has been magnified by a factor of X 3000.

What is the actual size of the cell?

To find the actual size of the cell:


  • The size of cells is typically measured using the micrometre (μm) scale, with cellular structures measured in either micrometers (μm) or nanometers (nm)
  • When doing calculations all measurements must be in the same units. It is best to use the smallest unit of measurement shown in the question
  • To convert units, multiply or divide depending if the units are increasing or decreasing
  • Magnification does not have units

Converting units of measurement


  • There are 1000 nanometers (nm) in a micrometre (µm)
  • There are 1000 micrometres (µm) in a millimetre (mm)
  • There are 1000 millimetres (mm) in a metre (m)

Worked Example


Step 1: Check that units in magnification questions are the same

Remember that 1mm = 1000µm

2000 / 1000 = 2, so the actual thickness of the leaf is 2 mm and the drawing thickness is 50 mm

Step 2: Calculate Magnification

Magnification = image size / actual size = 50 / 2 = 25

So the magnification is x 25