Converting Between Units (Cambridge (CIE) IGCSE Biology): Revision Note
Exam code: 0610 & 0970
Converting between units: Extended
Extended Tier Only
Using millimetres and micrometres as units
The table below shows how millimetres are related to two other measures of length
Unit | Length in mm |
|---|---|
1 centimetre (cm) | 10 |
1 millimetre (mm) | 1 |
1 micrometre (μm) | 0.001 |
What this basically means is that 1 mm = 1000 µm and 1 cm = 10 000µm
Unit conversion is necessary in calculation questions where two values are given in different units. Both need converting into the same unit before the calculation can be carried out
Worked Example
Both values (2000 μm and 50 mm) have different units, so one value needs to be converted so that they have the same units
It doesn't matter which value is converted
2000 μm can be converted into 50 mm
Remember 1000 µm = 1 mm, so divide 2000 by 1000 to convert the leaf thickness from μm into mm
2000 / 1000 = 2
So the actual thickness of the leaf is 2 mm and the drawing thickness is 50 mm
Magnification = image size / actual size = 50 / 2 = 25
So the correct answer is a magnification is x 25
Remember there are no units for magnification!
Examiner Tips and Tricks
If you are given a question with two different units in it, make sure you convert them to the same unit before doing your calculation. If you don’t there is a good chance that your answer will be the same as one of the incorrect options in a multiple choice question so you may think you got it correct when, in fact, you haven’t!
The following diagram may help with unit conversion between mm and µm:
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