MicroscopySpec 4.1.1.5
In short
An electron microscope uses electrons instead of light, so it has much higher magnification and resolving power than a light microscope. This lets biologists see much finer detail, such as ribosomes and the internal structure of mitochondria and chloroplasts. Magnification is calculated with magnification = size of image ÷ size of real object, using the same units for both.
Microscopy techniques have developed over time. The first microscopes used light and lenses to magnify a specimen, and these light microscopes were improved with better lenses and the use of stains. Later, electron microscopes were developed. These use electrons instead of light.
An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
| Light microscope | Electron microscope | |
|---|---|---|
| Magnification | Lower | Much higher |
| Resolving power (resolution) | Lower | Much higher |
| Detail seen | Cells and larger sub-cellular structures such as the nucleus | Much finer detail, including the internal structure of mitochondria and chloroplasts, and ribosomes |
- Magnification
- How many times larger the image is than the real object.
- Resolving power
- The ability to distinguish between two points that are close together as separate points. Higher resolving power gives a sharper, more detailed image.
Magnification and resolution are not the same: making an image bigger does not add detail. Electron microscopes show more because their resolving power is higher.
Magnification calculations
Rearranged: real size = image size ÷ magnification, and image size = real size × magnification. Make sure the image and real object are in the same units before you divide, then convert at the end. Give the answer in standard form if appropriate.
Calculating magnification
A drawing of a cell is 45 mm wide. The real cell is 0.15 mm wide. Calculate the magnification.
- Both sizes are in mm, so no conversion is needed.
- magnification = 45 ÷ 0.15 = 300.
Answer: × 300
Calculating real size
A cell appears 12 mm wide in an image magnified × 400. Calculate the real width in µm.
- real size = image size ÷ magnification = 12 ÷ 400 = 0.03 mm.
- Convert to µm: 0.03 × 1000 = 30 µm.
Answer: 30 µm
Use the triangle trick: put image size on top, and real size and magnification below. Cover the one you want and you can see the calculation.
Written and checked against the AQA GCSE Biology (8461) specification · Updated October 2026