Module 2: Microscopy
These free OCR A Level Biology Microscopy revision notes have been written for specification points 2.1.1(a) and 2.1.1(f).
The properties of a microscope are determined by its magnification and resolution:
- Magnification: How many times larger an image appears compared to the original object’s size.
- Resolution: The level of detail which can be seen in an image.
The table below outlines the different types of microscopes:
| Microscope Type | Key Features | Limitations |
|---|---|---|
| Optical Microscope |
– Cheap, portable, easy to use – Can view live specimens – Stains increase contrast |
– Low resolution – Limited magnification |
| Confocal Microscope |
– High-resolution 2D and 3D images – Depth selectivity on thick specimens – Can view live cells |
– Expensive – Requires fluorescent tagging |
| Transmission Electron Microscope (TEM) |
– Very high resolution and magnification – Reveals internal structure |
– Specimens must be dead – Thin sectioning needed – Requires staining and vacuum |
| Scanning Electron Microscope (SEM) |
– 3D surface images – High magnification and detail |
– Specimens must be dead – Requires coating with conductive material – Vacuum environment |
Properties of Microscopes
The table below provides an overview of the key properties of each type of microscope:
| Type | Magnification* | Resolution | Wavelength | Cost | Ease of Use |
|---|---|---|---|---|---|
| Optical | ×1500 | 200 nm | 400 – 700 nm | Cheap | Portable and easy |
| Confocal | ×2000 | 200 nm | 400 – 700 nm | Moderate | Less portable and medium |
| Scanning | ×100,000 | 0.2 nm | 0.004 nm | Expensive | Bulky and difficult |
| Transmission | ×500,000 | 0.2 nm | 0.004 nm | Expensive | Bulky and difficult |
*These are approximate values most commonly cited in examination materials.