Electron Microscopy Higher

Electron Microscopy Higher

Light microscopes are limited by the wavelength of visible light, which means they cannot resolve (distinguish) structures smaller than about 200 nanometres. This is why many organelles, such as ribosomes and the detailed inner membrane structure of mitochondria, cannot be seen under a light microscope.

Electron microscopes use beams of electrons instead of light. Electrons have a much shorter wavelength, giving electron microscopes far higher resolution — around 0.2 nanometres.

There are two main types:

• Transmission Electron Microscope (TEM): Electrons pass through a very thin slice of the specimen, producing a 2D image of internal structures. Shows great detail of organelles inside cells.
• Scanning Electron Microscope (SEM): Electrons bounce off the surface of the specimen, producing a detailed 3D image of the external surface. Used to study cell surface features and tissue structure.

Key limitation: Specimens must be dead and viewed in a vacuum — living cells cannot be observed. Preparation can also introduce artefacts (false structures from the preparation process).