We are all familiar with light microscopes, especially the compound microscope. We have seen plenty of this during our years in school, and even on television, perhaps at work as well. So, we have a general idea on what it is and how it works.
But, what about electron microscopes? You may or may not have heard of it, and you’re definitely bound to be curious as to just what it can do. To help you understand, here is a rundown of the differences between a light microscope and an electron microscope.
Type of microscopy
The main difference of light microscopes and electron microscopes is the type of microscopy that is employed to operate the microscope and render the magnified image of the specimen.
Most types of light microscopes make use of an imaging technique known as bright field microscopy. It works by using a light source attached on the microscope to emit a focused ray of light that illuminates the specimen from below so that its magnified image can be viewed through the eyepiece above.
This is an elementary form of microscopy that is used by many different types of microscopes. The contrast of the magnified image depends on the specimen’s absorption of light, and its resolution is dependent on the quality and focus of the light being used.
On the other hand, electron microscopes operate through a more advanced and sophisticated imaging technique called electron microscopy, which uses a beam of accelerated electrons to “illuminate” the specimen. How it works exactly depends on the type of electron microscope.
The beam of electrons coming from an electron gun can either be transmitted through the specimen, similar to how a light microscope works, or the microscope can scan the low and high energy electrons being emitted from the specimen as it is hit by the electron beam.
How it works
Because of the difference in microscopy techniques, as well as in physical structure, light and electron microscopes function somewhat differently when imaging a specimen.
Light microscope – One good thing about light microscopes is that these are fairly easy to use, which is partly why they are abundant, and are used in many science classrooms. The specimen just needs to be mounted on a microscope slide, which is then loaded onto the microscope stage.
Then, light from the illuminator passes through the microscope’s diaphragm and condenser, through the aperture and through the specimen, then all the way through the objective lens, body tube, and right through the eyepiece.
Electron microscope – Meanwhile, electron microscopes are a tad more complicated. For one thing, the specimen must undergo a rigorous procedure of specimen preparation which may include dehydration, staining, and gold plating, before being loaded inside a vacuum chamber.
Afterwards, this is where the magic happens, as the specimen is bombarded by a controlled electron beam from the electron gun, then the emitted electrons are collected by a detector, and a high-speed camera generates the specimen’s image.
The main function of any microscope is to magnify the image of a specimen, and as such, it is important to take into account the microscope’s maximum magnification level.
Light microscope – The magnification power of a light microscopy may range from as low as 40x to a maximum of 2000x magnification. This is the maximum number of times that the specimen image can be magnified, and it is usually achieved by using a compound lens system.
What produces this magnification is the objective lens of the microscope, as well as its eyepiece or ocular lens, which is also equipped with some level of magnification. Higher magnification light microscopes normally make use of immersion oil objective lenses with a high refractive index that can better focus the light and prevent distortion.
Electron microscope – Considered as the type of microscope with the highest magnification, electron microscopes have a magnifying power of 500,000x magnification or more, enabling us to see the smallest details on any given specimen that can’t be seen under any other type of microscope.
To make this possible, the electron microscope is engineered with a strategically shaped magnetic field that generates its special electron optical lens systems, which are what acts as the microscope’s high powered magnifiers.
Arguably just as important as the microscope’s magnification is its resolution or resolving power, which is what makes it possible to see the details of a magnified image clearly.
Light microscope – In terms of resolution, light microscopes are capable of low to average resolution levels, just enough to be able to see some details on specimens as small as 200 nanometers in size. This is mainly because of the microscope’s use of visible light, which has a wavelength of 400 to 700 nanometers.
The resolution of a light microscope can be somewhat increased by better focusing the light, widening the opening of the light source and thereby increasing the amount of light coming through, and using different types of light with a shorter wavelength.
Electron microscope – More than its high magnification capability, an electron microscope also has the highest resolving power out of all types of microscopes, with a capacity to distinguish details of a specimen down to the single nanometer.
This microscope can be used to look at minute specimens that are less than 300 nanometers in size, mainly since it utilizes electrons rather than photons, and these electrons have a wavelength that is thousands of times shorter than that of visible light.
Specimens that can be viewed
Not all microscopes can be used to view just any type of specimen, so it is important to understand what specimens are compatible with which microscope.
Light microscope – Most light microscopes are interchangeably referred to as biological microscopes, since these are mainly used to view and analyze organic materials and living specimens, such as small sections of various organisms, and different kinds of microorganisms.
It can also be used to study cells and tissue sections, various fluids such as blood and natural water, organelles, chromosomes, and even bacteria. With a light microscope, you will be able to see details such as macromolecules and cell parts, as well as observe the behavior of microorganisms.
Electron microscope – With electron microscopes, however, it’s possible to look at almost any type of material, whether organic or inorganic, meaning, these can be used to analyze plant and animal parts, liquid and gaseous substances, chemical compounds, various particulates, and so on.
The only downside is that most types of electron microscopes require the use of a vacuum chamber, which means that organic specimens cannot be studied while they are alive, and rigorous sample preparation must be performed beforehand.
What you can see
The microscope’s magnification and resolution are the two most important features that determine the kind of detail and information that a microscope is able to provide.
Light microscope – Since light microscopes have a somewhat average magnification level and resolving power, there is a limit on what sorts of things can be seen through the microscope, and how much detail can be presented.
For larger objects, certain parts and sections may be analyzed, while for smaller materials, intricate details such as molecules, cellular structures, and even cell parts may be visible depending on the microscope’s capabilities.
Electron microscope – For electron microscopes, there is virtually no limit as to what can be imaged, which makes them highly valuable imaging tools that can offer a host of important information on almost any specimen or material.
Small microorganisms such as parasites can easily be viewed, and even better, the structural makeup of chemical compounds can also be mapped, individual crystals on particles of dust and rock can be seen. But the most important is that electron microscopes have the capacity to show us each individual atom of any material.
Size and housing
Various types of microscopes such as light microscopes and electron microscopes also vary in size and appearance, which affect how the microscope can be housed, as well as its portability.
Light microscope – When it comes to appearance, light microscopes are relatively small, lightweight, and portable devices that come up to about a foot tall and can be lifted with one hand- although it’s advisable to use both hands to support the microscope.
Thus, it can be placed just about anywhere, from home office labs, kids’ study areas, science classrooms, field laboratories, and fixed research labs. These microscopes can be moved around, transported, and stored when not in use.
Electron microscope – Contrarily, electron microscopes are gigantically large imaging tools that easily take up a whole room from floor to ceiling, and occupy a fairly wide expanse of space. Hence, these are mostly stationary devices that are sometimes even built on site.
Moreover, an electron microscope cannot be housed in just any spacious room. Its size and the way it operates necessitates that its housing facility be equipped with a secure system of magnetic field cancellation, which is partly why most electron microscopes are underground.
If you take the time to research the topic of light microscope vs electron microscope, you are bound to find out lots of information ranging from how they differ in terms of features and capabilities, operating techniques and tools, functionality, and so on.
In fact, you’ll also see that these two microscopes have a large disparity in terms of the specimens that the microscope can be used for, and even basic but important details such as their appearance, housing requirements, and price.