Magnification Calculations (AQA A Level Biology): Revision Note
Exam code: 7402
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

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

Examiner Tips and Tricks
Remember:
1000 nanometers (nm) = 1 micrometre (µm)
1000 micrometres (µm) = 1 millimetre (mm)
1000 millimetres (mm) = 1 metre (m)
It can be easy to forget that 1 cm is 10 mm so keep an eye out for this extra step when you are working with calculations that need conversions between cm and other units.
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
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