Microscope Operation

November 3, 2021

The optical microscope is one of the inventions that has marked a before and after in the history of science, especially in the field of biology and medicine.

The microscope is an instrument that allows observing objects that are not perceptible to the human eye. This is achieved through an optical system composed of lenses, which form and amplify the image of the object being observed. This term arises in the seventeenth century and derives from the Greek words mikrós (small) and skopéoo (to observe).

Operation of the optical microscope

The operating principle of an optical microscope is based on the property of some materials that allow the direction of light rays to be changed. This allows to manufacture lenses

capable of converging or diverging light rays. By combining these lenses, an enlarged image of any object can be generated. The

A simpler example would be to use a single lens, such as a magnifying glass, to produce a magnified image of a sample.

In the case of an optical microscope, the magnified image is generated from different lenses. Some of them mounted on the microscope objective and others on the eyepiece. First, the objective lenses generate a real magnified image of the sample. This real image is then enlarged by means of the eyepiece lenses, giving rise to a virtual image that is larger than the original sample.

The other essential element for the operation of the optical microscope is light. It is for this reason that optical microscopes are equipped with a light bulb and a condenser to focus a beam of light onto the sample. Once the light has passed through the sample, the lenses are responsible for deflecting this light correctly to generate the magnified image.

How the compound microscope works

The following figure schematizes the operation of a compound microscope based on two lenses. The lens located near the sample is called objective, the eyepiece is the lens through which we observe the sample with the eye. The light from the sample passes through the objective forming a magnified image as a result. This image is called a real image. When looking through the eyepiece, you see a magnified image of the real image, known as a virtual image.

The simplest configuration of a compound microscope consists of one lens for the objective and one for the eyepiece. However, today microscopes include more lenses to correct for the various aberrations produced by simple lenses.

Furthermore, it is common for the light beam coming from the objective to be divided by means of an optical prism in order to be able to observe the sample with two eyepieces. Observing the sample with both eyes simultaneously results in greater comfort. This type of microscope is known as a binocular. In microscopes that do not include a prism to split the light, the sample must be viewed through a single eyepiece. These are monocular microscopes.

Representation of the operation of the microscope

Compound microscope magnification

The total magnification obtained using a compound microscope is the result of combining the magnification obtained by the objective with the magnification obtained by the eyepiece. Typically, most of the magnification occurs at the target. Total magnification is calculated by multiplying objective magnification by eyepiece magnification.

Compound microscopes usually come equipped with three or four objectives that can be selected using the nosepiece. The magnifications of these objectives are usually contained in a range between 4x and 100x. In the case of eyepieces, the magnification is usually between 5x and 20x. Based on these numbers the magnification achievable by the compound microscope varies between 20x and 2000x. However, due to the nature of light, the maximum magnification achievable by an optical microscope is limited to around 1500x.

Microscope care

The microscope is a valuable instrument. In order for it to serve effectively year after year, it needs proper care. For this reason, remember the following indications:

  • Avoid moving the microscope when the lamp is on, as the filament of the incandescent lamp is extremely sensitive.
  • To move it remotely, use the corresponding fixing screws.
  • Do not touch the lenses of eyepieces and objectives with your fingers, to avoid staining them with their natural oil.
    Do not move your microscope or lenses.
  • After using the microscope, clean it with a dust-free linen cloth or cotton wool. Check that they have not been prepared on the platen.
  • Leave it with the lowest magnification lens, the stage as close as possible to it, and protected with the corresponding cover.
Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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