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Microscopes and magnification
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Cells are tiny, so we need microscopes and some careful maths with units to study them.
Magnification
magnification = image size ÷ real size
Both sizes must be in the same unit before you divide.
Magnification has no unit. Write it like ×400.
Both sizes must be in the same unit before you divide.
Magnification has no unit. Write it like ×400.
Units of size
1 mm = 1000 µm (micrometres)
1 µm = 1000 nm (nanometres)
To go from mm to µm, multiply by 1000.
1 µm = 1000 nm (nanometres)
To go from mm to µm, multiply by 1000.
Light and electron microscopes
Electron microscopes have much higher magnification and resolution than light microscopes.
Resolution is the ability to tell two points apart. Higher resolution shows more detail, such as ribosomes and the inside of mitochondria.
Resolution is the ability to tell two points apart. Higher resolution shows more detail, such as ribosomes and the inside of mitochondria.
A drawing of a cell is 30 mm long. The real cell is 0.06 mm long. Find the magnification.
- Both are in mm, so you can divide straight away.
- magnification = 30 ÷ 0.06
- = 500
Answer: ×500
magnification = image size ÷ real size, with both in the same unit. Rearrange to real size = image size ÷ magnification. Electron microscopes give higher magnification and resolution.
The interactive lesson includes the diagrams for this topic.
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