Microscopy – OCR A Level Biology Revision Notes

Free Microscopy revision notes for OCR A Level Biology – covering 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

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.

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