The electron microscope and biological advancement.

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Toby Nicholson

The electron microscope and biological advancement

What is an electron microscope?

        An electron microscope does a similar job to an ordinary optical microscope that many people will have used before - it makes objects appear bigger. This is called magnification and lets one see details of very small objects, such as cell structures, which cannot be seen with the naked eye. In a normal optical microscope this is achieved by using higher-power lens that magnify the image more times.

However, there comes a point at which magnification of an optical microscope does not show more detail. This is to do with the physical nature of light. Light is made up of particles (called photons) that travel in a wave. We can only see that two objects are separate if light can pass between them. Light can pass between the letters on this page so you can see them. When objects are very close together light cannot pass through them and they appear as one object. You have experienced this phenomenon when a car heads towards you at night, at first it appears as one light but as it approaches it’s head lights split into two headlights. This ability to distinguish between objects is called resolution. The size of wavelength of light limits its resolution to about 2μm, the size of large bacteria.

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Electrons have a much smaller wavelength than light. This means that they can pas between objects that are too close together to let light pass them. Therefore electrons can resolve objects that light cannot. Microscopes that use electron instead of light are called electron microscopes and can resolve to about 1nm (smaller than a haemoglobin molecule). There are two types of electron microscopes, transmission electron microscopes which pass beams of electrons through very thin objects and, scanning electron microscopes which beams of electrons of the surface of an object

(Indge, B etal 2000).

What can electron microscopes do?

        Electron ...

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