The world of microorganisms is fascinating, from microscopic parasites like the liver fluke to staphylococcus bacteria and even organisms as minuscule as a virus, there is a microscopic world waiting for you to discover it. Which type of microscope you need to use depends on what organism you are trying to observe.
Most student microscopes are classified as light microscopes. Some cutting-edge types of light microscopy can produce very high-resolution images.
However, if you want to see something very tiny at a very high resolution, you may want to use a different, tried-and-true technique: electron microscopy.
What are the key differences between light and electron microscopes?
Light microscopes, also called optical microscopes, use visible light and lenses to magnify objects. They are typically used to view transparent or translucent samples and have a maximum magnification of around 1000x.
Electron microscopes, on the other hand, use a beam of electrons to create an image of a specimen. They can magnify objects up to a million times, making them much more powerful than light microscopes.
There are two main types of electron microscopes: transmission electron microscopes (TEM) and scanning electron microscopes (SEM). TEMs use an electron beam to create a detailed image of the sample, while SEMs use an electron beam to create a 3D image of the sample’s surface.
There are several key differences between light and electron microscopes:
- Magnification: Light microscopes can magnify objects up to about 1,000 times their original size, while electron microscopes can magnify up to about 100,000 times.
- Resolution: The resolution of a microscope refers to the level of detail that can be seen in an image. Electron microscopes have a much higher resolution than light microscopes, allowing them to see much finer detail.
- Sample preparation: Light microscopes can be used to view living organisms, while electron microscopes require special sample preparation, often drying or embedding in resin.
- Costs: Due to the complex technology, electron microscopes are significantly more expensive than light microscopes.
- Size: Electron microscopes are much larger and heavier than light microscopes.
What is The compound light Microscope?
A compound light microscope is a microscope with more than one lens and its own light source. In this type of microscope, there are ocular lenses in the binocular eyepieces and objective lenses in a rotating nosepiece closer to the specimen.
Although sometimes found as monocular with one ocular lens, the compound binocular microscope is more commonly used today.
The compound light microscope uses optical lenses to bend light and magnify microscopic specimens. The lenses used are objective lenses, which have varying magnifications, and ocular lenses, which have fixed magnifications. These microscopes are great for observing single-celled organisms such as tiny parasites and many types of bacteria.
What is the Maximum Magnification that can be archived with the Compound Light Microscope?
To determine the total magnification when using a compound microscope, multiply the magnification of the objective lens by the ocular lens. For example, if you are observing a specimen using a 10 times magnification objective lens with a ten times magnification ocular lens, you are seeing the specimen at 100 times magnification.
Because of resolution (the ability to distinguish between two separate points), a compound microscope has a maximum observable magnification of 2,000 times.
In order to ascertain the total magnification when viewing an image with a compound light microscope, take the power of the objective lens which is at 4x, 10x, or 40x and multiply it by the power of the eyepiece which is typically 10x.
Therefore, a 10x eyepiece used with a 40x objective lens will produce a magnification of 400x. The naked eye can now view the specimen at magnification 400 times greater and so microscopic details are revealed. More on objective lenses here.
Magnification is the ability to view an object as larger. A good image is obtained when the amount of specimen detail is also increased. Magnification alone will not achieve this.
What is Electron Microscope?
Instead of using lenses and light to magnify a specimen, The electron microscope uses a beam of electrons and their wave-like characteristics to magnify an object’s image, unlike the optical microscope which uses visible light to magnify images.
Electron microscopes are used to investigate the ultrastructure of a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals.
Industrially, electron microscopes are often used for quality control and failure analysis. Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the images.
One limitation, however, is that electron microscopy samples must be placed under a vacuum in electron microscopy (and typically are prepared via an extensive fixation process). This means that live cells cannot be imaged.
There are two major types of electron microscopy. In scanning electron microscopy (SEM), a beam of electrons moves back and forth across the surface of a cell or tissue, creating a detailed image of the 3D surface.
In transmission electron microscopy (TEM), in contrast, the sample is cut into extremely thin slices before imaging, and the electron beam passes through the slice rather than skimming over its surface. TEM is often used to obtain detailed images of the internal structures of cells.
What is the Maximum Magnification that can be archived with the Electron Microscope?
Wavelengths influence resolution. Because a compound microscope uses light, its resolution is limited to .05 micrometers. As the wavelength of an electron can be up to 200,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects.
A scanning transmission electron microscope has achieved better than 50 pm resolution in annular dark-field imaging mode and magnifications of up to about 10,000,000x whereas most light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000x
Light Microscope vs Electron Microscope
|Light Microscope||Electron Microscope|
|Uses light (approx 400-700 nm) as an illuminating source||Uses electron beams (approx 1 nm) as an illuminating source|
|Lower magnification than an electron microscope||Higher magnification|
|No risk of radiation leakage||Risk of radiation leakage|
|Specimen preparation takes about a few minutes or an hour||Specimen preparation takes several days|
|Both live and dead specimens can be seen||Only dead and the dried specimen can be seen|
|The image formation depends upon the light absorption from the different zones of the specimen||The image formation depends upon the electron scattering|
|The image is seen through the ocular lens. No screen needed||The image is received on a zinc sulfate fluorescent screen|
|Useful magnification of 500x to 1500x||Direct magnification is as high as 16000x and photographic magnification is as high as 1000000 x|
|Low resolution||High resolution|
|Inexpensive and requires a low maintenance cost||Expensive and high maintenance|
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