Types of Microscopes and Their Magnifications

To enable scientists to see and observe microorganisms, microscopes were invented. The word microscope comes from the Latin word micro, which means small, and the Greek word skopos which means, to look at (Tortora et al., 2008). With the advances in technology, the microscope has also evolved and more types are added into the list. With the need to study the organelles of cells and microorganisms, more powerful microscopes are invented.

Basically, a microscope consists of two magnifying lenses, the objective and the eyepiece or ocular. The total magnification is computed by multiplying the magnifications of these two lenses. For example, the total magnification of an object as observed using a 10x ocular and a 40x objective is 400 times (Tortora et al., 2008).  To determine what microscope should be used to observe a particular microorganism or cell, understanding the types of microscopes and their magnifications is very important.

Compound Light Microscope

Both stained and unstained specimens can be examined using this microscope. It uses visible light as its source of illumination (Turgeon, 2007). This type of light has a long wavelength and cannot resolve structures smaller than 0.2 um. With this and other considerations, the magnification achieved by even the best compound light microscopes is only until 2000 times. However, most microscopes have three objectives with the following magnification power: 10x (low power), 40x (high power), 100x (oil immersion) (Tortora et al., 2008).

Phase Contrast Microscope

Phase contrast microscopy is useful in examining internal structures of living microorganisms. Its principle is based on the wave nature of light rays. It uses a special condenser containing an annular diaphragm. The diaphragm allows light to pass through the condenser and focuses the light to hit the specimen and the diffraction plate in the objective lens. Direct and reflected or diffracted light rays are brought together to produce an image. It has a total magnification of 100 to 1,000 times (Tortora et al., 2008).

Electron Microscopes

The principle behind electron microscopy is the same as that of brightfield microscopy. However, instead of a beam of light, the specimen is illuminated with a beam of electrons. This beam is concentrated onto the specimen, and the objective provides the primary magnification (Turgeon, 2007). There are two general types of electron microscopes: scanning and transmission. The main difference between the two is that transmission electron microscopes (TEMs) produced a two-dimensional image and can magnify objects from 10,000 to 100,000 times, while scanning electron microscopes (SEMs) produce an image that is magnified 1,000 to 10,000 times and appears three-dimensional.

Scanning Tunnelling Microscope (STM)

This type of microscope uses a tungsten probe that scans the specimen and reveals the elevations and depressions of the atoms on the surface of the specimen. It can magnify objects that are about 1/100 the size of an atom.  STMs are used to provide very detailed images of molecules such as that of deoxyribonucleic acid or DNA. (Tortora et al., 2008).

Atomic Force Microscope (ATM)

ATMs make use of a metal-and-diamond probe that is forced down onto a specimen. As it moves on the surface of the specimen, its movements are recorded and a three-dimensional image is produced. They are used to magnify images of biological substances as well as to document molecular processes such as the formation of fibrin strands during blood coagulation (Tortora et al., 2008). The maximum magnification for an ATM is about 2000 times (Advanced Surface Microscopy Inc.).

Microscopes have been an indispensable tool in different fields of science. To maximize the use of microscopy, knowledge of its different types and magnifications is not the only requirement. Proper care and maintenance is also very important to keep your microscope in its optimum condition.
Bibliography

  • Advanced Surface Microscopy Inc. (n.d.). Atomic Force Microscopy. Retrieved October 29, 2011, from Advanced Surface Microscopy Inc.: http://www.asmicro.com/applications/afmpage.htm
  • Tortora, G. J., Funke, B. R., & Case, C. L. (2008). Microbiology: An introduction (9th ed.). Singapore: Pearson Education South Asia Pte Ltd.
  • Turgeon, M. L. (2007). Linne and Ringsrud’s Clinical Laboratory Scienc: The Basics and Routine Techniques (5th ed.). Singapore: Elsevier Inc.
VN:F [1.9.22_1171]
Rating: 10.0/10 (1 vote cast)
VN:F [1.9.22_1171]
Rating: +1 (from 1 vote)
Types of Microscopes and Their Magnifications, 10.0 out of 10 based on 1 rating

Previous post:

Next post: