Magnification Formula (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note
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Magnification Formula
Magnification can calculated using the following formula:
magnification = image size ÷ actual size
This formula can be entered into an equation triangle to aid memory and allow for easy rearranging:
The triangle allows the formula to be rearranged as follows:
Magnification = image size ÷ actual size
Actual size = image size ÷ magnification
Image size = magnification x actual size
When using the magnification formula it is essential that any units used in the calculation are the same, e.g. if the size of an image is measured in mm then the actual size of the object must also be in mm within the calculation
Note that magnification does not have any units and is just written as, e.g. x10 or 5000x
Worked Example
An image of an animal cell measures 30 mm with a ruler and has been magnified by a factor of x3000.
What is the actual size of the cell?
Examiner Tips and Tricks
This skill most often comes up in papers 5 and 6, though it sometimes appears in multiple choice and the theory paper.
Remember the following when carrying out magnification calculations:
Always look at the units that have been given in the question - you will usually be expected to measure objects in mm rather than in cm - double check the question to see!
Learn the equation triangle for magnification
Don’t forget that magnification has no units - students often lose a mark because they put one in
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