Different Types Of Microscopes

A look at the different types of microscopes and what they are used for.

There are four main types of microscopes that a biologist uses: dissection, compound, Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM).

There is certain terminology used when discussing microscopes. Magnification is referring to the

ratio of the size seen in the microscope to the actual size of the specimen. On a compound microscope it is usually between 4x and 100x. Resolution is the clarity and detail seen. It is the minimal distance between two points in which they can be seen separately (i.e.: not blurred). Field of view refers to how much you actually see when looking in a microscope. As field of view increases, magnification decreases. Depth of field is the number of layers you see. Total magnification is the product of the objective lens and the ocular (10x). Parfocal is a term used when describing compound microscopes. this means that the focus is maintained when changing the magnification. This way you don't have to re-focus when changing powers.

A dissection microscope is light illuminated. The image that appears is three dimensional. It is used for dissection to get a better look at the larger specimen. You cannot see individual cells because it has a low magnification.

A compound microscope is also light illuminated. The image seen with this type of microscope is two dimensional. This microscope is the most commonly used. You can view individual cells, even living ones. It has high magnification (from 4x - 100x). However, it has a low resolution.

SEM use electron illumination. The image is seen in three dimension. It has high magnification and high resolution. The specimen is coated in gold and the electrons bounce off to give you and exterior view of the specimen. The pictures are in black and white.

TEM is also electron illuminated. This gives a two dimensional view. Thin slices of specimen are obtained. The electron beams pass through this. It has high magnification and high resolution.

A compound microscope contains twelve basic parts. The ocular is the eye piece. It is what you view through. It contains a lens of with a magnification of 10x. The ocular is attached to the body. The body, also called the barrel, contains a mirror to view the image at an angel. The arm of the microscope is used as a handle when moving microscopes. It extends from the body to the base (which I will discuss shortly). The nosepiece holds the objective lens and is attached to the body. The objective lens magnifies by the power. The mechanical state is where the slide goes. It can be adjusted accordingly. The diaphragm controls the amount of light. The condenser focuses the light on the image. The light source is whit light used to illuminate the specimen. The coarse adjustment focuses on low powers while the fine adjustment is used to focus on high lenses. The base holds the light source.

To operate a microscope properly, you should follow some simple steps. First you must plug it in and turn it on. Make sure it is set on the lowest power. Move the stage to the top position.

Place the slide on the stage agist the corner. Adjust the stage. Use the coarse adjustment to get the image in focus. Use the fine adjustment to see more detail. Finally move the lens clockwise to move to higher magnification. Your specimen should be seen clearly in focus even when changing powers.

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