Microscopes are widely used equipment in all branches of science, and you must have gone through the terms light, compound, and electron microscopes. Optical and electron microscopes are essential and in use in the fields of physics, biology, and other domains these days. Optical microscopes including stereo and compound microscopes are inevitable to study the components of organisms. Moreover, electron microscopes offer a more detailed examination. However, their working principle and produced results vary considerably.
Let’s tell you more about these two types: electron and optical microscopes in detail.
Table of Contents
Comparison Table
| Characteristics | Electron Microscope | Optical Microscope |
| Magnification | 1 to 50 million times | 2500 times |
| Light Source | Electron beam | LED/ halogen light |
| Types | Transmitted EM & Scanning EM | Compound and Stereo microscope |
| Lenses | Electromagnetic | Achromatic objectives and eyepieces |
| Specimen preparation | Hours or days | Minutes |
| Image formation | Zinc sulphate fluorescent | Eyepiece |
| Cell Observation | Living cells | Dried specimen |
| Molecule Observation | Yes | No |
| Portability | Not portable | Portable |
| Cost | High | Low |
Electron Microscope
Electron microscopes differ from light microscopes and are generally used in research labs to inoculate molecules. They are much more advanced and use a beam of electrons to illuminate the specimen instead of visible light. Electron microscopes are quite expensive and used to examine objects that need detailed observation. It provides magnification of several hundred thousand to check the intricate details. Nanobiologists and chemists utilize electron microscopes to study the properties of molecules.
History
Ernst Ruska and Max Knoll produced the electron microscope in 1931 despite the development of the first electromagnetic lens in 1926 by Hans Busch.
Reinhold Rudenberg acquired the patent for the electron microscope the same year and started working on the production of the microscope by Siemens-Schuckertwerke.
The first-ever microscope could magnify objects up to four hundred power. Ernst Ruska created a new electron microscope model in 1933 that could produce a higher resolution. Helmut Ruska and Bodo von Borries made the examination of biological samples possible in 1937. Ernst Ruska received the Nobel Prize in Physics for developing the electron microscope.
Furthermore, the first commercial electron microscope was released by Siemens-Schuckertwerke to the public in 1938.
Illumination Source
Unlike how compound microscopes work, electron microscopes use an electron beam in place of natural light to illuminate the sample. The electrons are emitted from the cathode and behave like photons to brighten the specimen. The wavelength of the electrons allows them to show more details of the object under study.
Lenses
Electron microscopes contain an electromagnetic lens that produces electric and magnetic fields which guide the electrons. The electrons form a thin, compact beam passing through the electromagnetic lens. It enables the electrons to create an amplified effect by directing the converged beam onto the specimen.
Magnification
Electron microscopes helps magnify the specimen between 1 and 50 million times to reveal the intricate details of the sample. This high magnification allows you to observe cells, molecules, biopsy samples, and microorganisms. It also enables the examination of organelles like mitochondria and ribosomes.
Imaging
Electron microscopes produce incredibly intricate colored images of the samples without staining. The specimens are coated with electrons to allow in-depth examination. However, it may require days to prepare a sample for observation in the electron microscope.
Limitations
Despite the superiority of electron microscopes over compound and stereo microscopes, they cannot observe live samples. The bombardment of electrons kills the live specimen. Thus, electron microscopes are not the best choice if you want to study a live organism or tissue.
Optical Microscopes
Optical microscopes, also known as light microscopes, are generally used to examine microorganisms. It allows you to study germs and other microbes that you might not see with the naked eye. These light microscopes, unlike the stereo microscopes, use LED light to illuminate the object and see it through the eyepiece. They are the best choice for examining living cells and tissues.
History
The concept of magnification goes back to 1538 when Italian physician Girolamo Fracastoro mentioned that two spectacle glasses superimposed on each other would make things seem larger. It was a simple microscope, which then went to an advanced form, called light microscope and the invention went on. The first-ever optical compound microscope came into being in 1590, thanks to Hans Jansen, his son Zacharias Jansen, and Hans Lippershey.
This microscope comprised an eyepiece and objective lens to produce the magnified image. With continuous advancement, Benjamin Martin created color-corrected lenses in 1774. Dutch optician Francois Beeldsnijder enhanced the optical microscope experience in 1791 by introducing achromatic lenses with less distortion and more clarity.
Illumination
The first optical microscopes used natural light to observe objects. But, modern optical microscopes make use of a more steady light source. Optical microscopes now contain an LED or halogen light source passing through the condenser to brighten the specimen. The microscopes may have an incident or transmitted illumination.
Lenses
Optical microscopes typically have a set of eyepieces and objective lenses. The objective lenses magnify the sample through its switchable magnifications, which are then taken by the eyepieces or ocular lenses to produce the image. The number of lenses depends on using a monocular, binocular, or trinocular microscope. Each refers to one, two, or three eyepieces, respectively.
Magnification
The magnification of optical microscopes is not as high as electron microscopes. An optical microscope may enlarge the object to 2500x compared to a million magnifications by electron microscopes. Eyepieces are usually available in two magnifications. On the other hand, every other microscope has four objective lenses. The combined action of objective and ocular lenses produces the total magnification. Compound microscopes offer a wide range of magnification due to multiple types of microscope lenses.
Imaging
Optical microscopes basically produce black-and-white images, but the specimens under observation in optical microscopes are still stained before observation. It allows the observer to study and understand the different aspects of the object. It also identifies the characteristics of bacteria according to their staining properties.
Limitations
While you can observe living cells in optical microscopes instead of electron microscopes, they also have a few limitations. Foremost, optical microscopes cannot magnify the samples above a few hundred. The commonly used optical microscopes in labs have a magnification of up to 2500x. Moreover, you cannot observe the molecular properties of the samples under optical microscopes due to restricted magnification.
Differences Between Electron and Optical Microscopes
Definition
Electron microscopes utilize electron beams to produce images of high magnification.
On the other hand, optical microscopes observe specimens at comparatively lower magnification.
Magnification
Electron microscopes magnify the specimen between 1 and 50 million times to reveal the intricate details of the sample.
In contrast, optical microscopes only magnify objects up to 2500x microscopes. The observation is not as high as an electron microscope.
Light Source
Electron microscopes use electrons emitted from a cathode to illuminate the sample. The electrons are less than 1nm and act as photons.
Alternatively, optical microscopes brighten the samples through a halogen or LED illumination source. The light emitted is between 400 – 700 nm.
Types
Electron microscopes are basically of two types; scanning electron microscope and transmission electron microscope.
Optical microscopes may be divided into various categories. They are widely categorized as compound microscopes and dissecting (stereo) microscopes.
Lenses
Electron microscopes have electromagnetic lenses that guide the electron beam and produce an image on the screen.
While optical microscopes comprise objective and eyepiece lenses. The total magnification is obtained by the combined action of both lenses.
Specimen Preparation
Preparing a specimen for electron microscopy can take a few hours to days. The process takes more time due to dehydration and drawing.
Contrarily, optical microscope sample slides can be prepared within a few minutes by staining.
Image Formation
The image formation in electron microscopes depends on electron scattering, and the images appear on the zinc sulfate fluorescent screen.
In the meantime, image formation in optical microscopes depends on light absorption, and the images are observed on the eyepiece.
Cell Observation
Electron microscopes observe minute details of organisms up to the molecular level.
On the other hand, optical microscopes allow you to study living cells that you cannot examine in electron microscopes.
Radiation Leakage
Electron microscopes carry a risk of radiation leakage due to the use of electrons for illumination.
However, optical microscopes do not risk radiation leakage as the illumination source does not contain radiation.
Portability
Electron microscopes are large in size and are placed in research labs. Thus, they are not portable.
Optical microscopes are comparatively small and portable and are also available in pocket size. Battery-operated optical microscopes can be used anywhere conveniently.
Cost
Electron microscopes cost quite a lot and require high maintenance. Any damage to the electron microscope will require high costs.
Whereas optical microscopes do not cost as much as electron microscopes. Their maintenance costs are also comparatively low.
Observable Samples
Electron microscopes help study the chemistry and molecular biology of the specimen. Moreover, these microscopes are the best for microbiology use.
Whereas optical microscopes help students and scientists understand living cells through magnified observation.
Application
Science enthusiasts, researchers, and students use optical microscopes to study objects in labs or at home.
On the other hand, electron microscopes in high-precision research labs facilitate the study of molecules and cellular details of biological and molecular samples.
The Bottom Line
Electron microscopes and optical microscopes are widely used in research labs and industries. Optical microscopes like SW380T and Leica A60 have applications in school and research labs. On the other hand, research laboratories utilize electron microscopes to observe cells and molecules. Electron microscopes offer a high magnification, while optical microscopes have comparatively lower magnification. Optical microscopes for children may encourage them to take an interest in science and nature.
Frequently Asked Questions
Why are electron microscopes better than optical microscopes?
Electron microscopes offer a much higher magnification than optical microscopes. Thus, they allow you to observe molecules and cellular levels of cells. You can also observe bacteria and viruses in-depth magnified a million times.
Can you see DNA with an optical microscope?
Yes. You can observe DNA under an optical microscope if stained properly. However, you may be able to study the detailed structure only under an electron microscope.
What is the most powerful microscope?
The transmission electron microscope is the most powerful electron with its ability to see the structure of cellular organelles. These microscopes enable you to see and study individual atoms. It is widely used in finding and developing new compounds.
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