What is the advantage of using high power on a microscope?

Since the invention of the first prototype in the early 20th Century the electron microscope has allowed us to peer into the micromolecular world more deeply than ever.

Image of blood clot using a scanning electron microscope.

By firing a concentrated “beam” of electrons at a sample (either a thin cross-section in the case of transmission electron microscopy or a three dimensional sample in the case of scanning electron microscopy) in a vacuum, biological and chemical structures can be revealed in ever more clarity, and a number of variations on the main techniques have been developed in recent decades.

Eye of a fruit fly, Drosophila melanogaster, scanning electron microscopy Image Credit: Heiti Paves / Shutterstock

As with any scientific technique or technology, it is not without its disadvantages, but it does have several advantages for the researcher using it. Some of these are listed below.

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Image of human neutrophils using a transmission electron microscope.

Advantages of electron microscopy

Electron microscopy has several main advantages. These include:

• Magnification and higher resolution – as electrons rather than light waves are used, it can be used to analyze structures which cannot otherwise be seen. The resolution of electron microscopy images is in the range of up to 0.2 nm, which is 1000x more detailed than light microscopy.
• Diverse applications – Electron microscopy has a diverse range of applications in many different fields of research including technology, industry, biomedical science and chemistry. Examples of applications include semiconductor inspection, computer chip manufacture, quality control and assurance, analysis of atomic structures, and drug development.
• High-quality images – With proper training, an electron microscope operator can use the system to produce highly detailed images of structures which are of a high quality, revealing complex and delicate structures that other techniques may struggle to reproduce.

Disadvantages of electron microscopy

However, there are several disadvantages which may mean that other techniques, especially light microscopy and super-resolution microscopy, are more advantageous to the researcher. These include:

• Inability to analyze live specimens – As electrons are easily scattered by other molecules in the air, samples must be analyzed in a vacuum. This means that live specimens cannot be studied by this technique. This means that biological interactions cannot be properly observed, which limits the applications of electron microscopy in biological research.
• Black and white images – Only black and white images can be produced by an electron microscope. Images must be falsely colorized.
• Artefacts – These may be present in the image produced. Artefacts are left over from sample preparation and require specialized knowledge of sample preparation techniques to avoid.
• Cost – Electron microscopes are expensive pieces of highly specialized equipment. As most projects have limited budgets, it may prove detrimental to use an electron microscope in the research. However, running costs can be similar to alternatives such as confocal light microscopes, so the investment in a basic electron microscope is still worth considering even if budgetary concerns are a major factor in decisions against utilizing the technology.
• Size – Despite the advantages in technology over the years, electron microscopes are still large, bulky pieces of equipment which require plenty of space in a laboratory. Also, as electron microscopes are highly sensitive, magnetic fields and vibrations caused by other lab equipment may interfere with their operation. Consideration must be given to this if the researcher is looking to install an electron microscope in their laboratory.
• Training – Specialist operators are required to operate electron microscopes, and these can undergo years of training to properly use this technology.

Electron microscopy: A highly useful analytical technique

These advantages and disadvantages must be carefully considered by researchers and project managers. However, electron microscopy is a highly useful analytical technique which remains at the forefront of scientific research and with the right training and use can produce results which no other technology available can.

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Last updated Oct 22, 2019

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Magnifying PowerA compound microscope has two sets of lenses. The lens you look  through is called the ocular. The lens near the specimen being examined is called the objective. The objective lens is one of three or four lenses located on a rotating turret above the stage, and that vary in magnifying power. The lowest power is called the low power objective (LP), and the highest power is the high power objective (HP).   You can determine the magnifying power of the combination of the two lenses by multiplying the magnifying power of the ocular by the magnifying power of the objective that you are using. For example, if the magnifying power of the ocular is 10 (written 10X) and the magnifying power of an objective is 4 (4X), the magnifying power of that lens combination is 40X.

Field of View (FOV)The field of view is the maximum area visible through the lenses of a microscope, and it is represented by a diameter. To determine the diameter of your field of view, place a transparent metric ruler under the low power (LP) objective of a microscope. Focus the microscope on the scale of the ruler, and measure the diameter of the field of vision in millimeters.  Record this number. 

When you are viewing an object under high power, it is sometimes not possible to determine the field of view directly. The higher the power of magnification, the smaller the field of view. 

The diameter of the field of view under high power can be calculated using the following equation:

For example, if you determine that your field of view is 2.5 mm in diameter using a 10X ocular and 4X objective, you will be able to determine what the field of view will be with the high power objective by using the above formula. For  this example, we will designate the high power objective as 40X.

Estimating the Size of the Specimen Under ObservationObjects observed with microscopes are often too small to be measured conveniently in millimeters.  Because you are using a scale in millimeters, it is necessary to convert your measurement to micrometers. Remember that 1 μm = 0.001 mm. 

To estimate the size of an object seen with a microscope, first  estimate what fraction of the diameter of the field of vision that the object occupies. Then multiply the diameter you calculated in micrometers by that fraction. For example, if the field of vision’s diameter is 400 μm and the object’s estimated length is about one-tenth of that diameter, multiply the diameter by one-tenth to find the object’s length.