Compare and contrast the use of light and electron microscopes in biological studies. Microscopes are laboratory equipment which are used to observe any matter that is too small to be seen by the naked eye. There are several types of microscopes – the two most common being the optical microscope, also known as a light microscope, and the electron microscope, which can be either a transmission electron microscope (TEM) or a scanning electron microscope (SEM). There are more differences than similarities between light microscopes and electron microscopes.
Firstly, optical microscopes and electron microscopes both work in different ways. As the light source or condenser of an optical microscope focuses light on a tiny bright spot of the specimen, the microscope accumulates light from the well-illuminated specimen in the stage of the microscope. The small objective lens then brings the image of the object into focus within the microscope’s tube, and is then magnified by a second lens, called an ocular lens or the eyepiece. The specimen in an optical microscope can be rather thick.
In contrast, unlike the light microscope, the electron microscope visualises objects using a thin beam of rapidly moving electrons that interfere with the specimen placed in the tube. In a TEM, the electrons are emitted by the electron gun in the cathode ray tube, and then accelerated by the anode. They then pass through a small aperture, which forms them into a beam, and into the vacuum inside the tube. The electromagnetic lenses around the tube of the electron microscope maintain the electron beam and focus it within the centre of the tube with an electromagnetic field. When the beam reaches the specimen, the electrons are either absorbed, scattered, or pass through it. Since different parts of the specimen would be variously transparent to electrons, different amounts of electrons with changed energy pass through these areas. The electrons are collected on fluorescent or...
Please join StudyMode to read the full document