Difference between Optical and Electron Microscope

The word microscope comes from the combination of two Greek words, “micros” which refers to small and “scópeo” which means to look. These instruments have been used in a more rudimentary way since the 13th century, in what we know today as magnifying glasses, which managed to considerably enlarge an image. But it was not until the end of the 16th century, when the Dutch eyeglass manufacturer Janssen manufactured the first compound microscope with two lenses mounted on a tube, which managed to enlarge the image up to nine times its original size. It is also said that Galileo Galilei designed an object that combined two lenses, one concave and one convex, for the same purpose. However, it was in the year 1625, when Faber first used the term microscope to refer to this instrument.

Although with the arrival of the Dutch scientist Antonie van Leeuwenhoek, in 1674 the quality of the microscopes existing up to that time was perfected, which allowed him to make great discoveries such as the bacteria and red blood cells present in the blood, which is why today he is known as the father of microbiology.

From that moment on, improvements in the optical microscope have not ceased, but in 1931 with the creation of the electron microscope, a giant step was taken for the world of science, which achieved with this instrument an image magnification of 100,000 x.

What is an Optical Microscope?

The optical microscope is an apparatus designed from different lenses that allow observing with a considerable increase in size, certain particles or elements that it is not possible to specify with the naked eye. The optical microscope is one of those great inventions that marks a before and after in fundamental areas for life as we know it today, and from its creation great advances arose in medicine, chemistry, physics, biology , among other; and it is that with its use it was possible to discover endless new particles that before the appearance of this instrument, it was not possible to detect them.

The operation of the optical microscope is due to the properties of the materials used in the lens, which are manufactured with a certain shape (convex and concave) and that, placed in alignment with the objective, allow the direction of light to be changed and generate a magnified image of any object. Another essential element in the optical microscope is light, since it must reach the sample efficiently so that the lenses fulfill their function of creating an image, which is perceived by the human eye with a larger size; For this reason, modern optical microscopes incorporate a light source.

Today the optical microscope is used in laboratories that require the study and analysis of the microscopic organization. Its maintenance and operation can be carried out by the same operator, so it is quite simple, although it must remain on a firm surface and it is necessary to clean frequently so as not to interfere with subsequent samples.

What is an Electron Microscope?

The electron microscope is an instrument that uses electrons to magnify images of small elements. Through the use of electron microscopes, magnifications of up to 5000 times more than with optical microscopes can be achieved, since the wavelength of the electrons is considerably shorter than that of the photons used in traditional instruments.

The electron microscope is made up of several essential parts for its operation:

Electron source: equivalent to the light source in the optical microscope, which when heating the atoms, the electrons increase and are directed towards the sample.
Electromagnetic lenses: they are used to generate electric and magnetic fields that, when interacting with electrons, cause them to diverge and converge at a point.
Vacuum chamber: both the source of electrons and the electromagnetic lenses must be in a vacuum chamber because when mixed with air, the trajectory of the electrons is not observed, therefore the enlargement of the image is not obtained. However, it is necessary that the sample to be observed must also be placed in a vacuum chamber, which makes it difficult to study live samples with the electron microscope.
Detector: it is a fluorescent screen against which the electrons impact and throw the image of the sample. Next, the information captured by the screen is transmitted to a computer to assign artificial colors and process the resulting image.

There are two different types of electron microscopes, depending on what you want to do with the sample. If the internal characteristics of an element are to be analyzed, it is necessary to use the transmission electron microscope. But if what is wanted is to know the dimensions of the sample from a three-dimensional image, a scanning electron microscope is required.