How does an optical microscope work
How does a microscope work?
A microscope magnifies very small things and structures. But how exactly does a (light) microscope work? In principle, the way it works is very simple: With the help of lenses, the light rays are refracted so that an optically enlarged intermediate image (so-called "real intermediate image") is created. This "real intermediate image" of the objective is then enlarged to form a "virtual intermediate image" with the aid of the eyepiece, which acts like a magnifying glass. It is also called a "compound microscope" because there are basically two magnification steps. (For a detailed explanation see below)
Unlike the Telescope, where things only appear small because of the great distance, you can use a microscope to enlarge things that are located a short distance in front of the eye.
The following graphic illustrates how a microscope works by following the course of the light. You can see that it penetrates at least two lenses - as a rule there are four, because nowadays both the objective and the eyepiece each consist of two lenses. In addition, you usually have to include the lens of the eye in the process - with the digital microscope, however, a camera is used instead of the eye.
The light is emitted from the light source. It penetrates the object that is on the slide that is clamped on the stage. The light rays are enlarged through the lens. An enlarged "real intermediate image" is created in the tube. This is clearly enlarged again by the eyepiece.
Understanding exactly how a microscope works requires some basic knowledge of optical phenomena. The following is a step-by-step derivation.
Transparent bodies refract light
Light moves through the vacuum at the speed of light. However, it is slowed down by solid substances (e.g. water or glass). In the figure below, the light is shown by dotted lines. It moves faster in the air than in glass.
When light hits an inclined transparent surface, it does not go straight through, but is deflected. This phenomenon is known as "light refraction", so the path of the light rays is deflected.
Principle of lenses (converging lenses, diverging lenses)
With the help of lenses, the refraction of light can be used in a targeted manner. There are basically two types of lenses: converging lenses (convex) and diverging lenses (concave).
First of all for Converging lens: their surfaces are convex. Rays of light. which fall parallel on the converging lens are refracted by the glass in such a way that they meet behind the lens at a common point. This point will too Focus called, the distance between the lens and the focal point is called Focal length.
Exactly the other way around is the case with one Diffusing lens. Your surface is concave arched. The light rays falling parallel on the lens are deflected apart. It is called "scattered". With the light microscope, however, only the functionality of a converging lens is relevant.
For the sake of completeness, here is how a diffusing lens works:
More about the difference between concave and convex (including motto).
How a magnifying glass works
To understand how a microscope works, one must first think about magnifying glasses. A magnifying glass is a collecting lens, usually on a handle. But why does a magnifying glass enlarge? The solution to the riddle is a "virtual image", which is generated by the lens. This enlarged virtual image is then displayed correspondingly larger on the retina in the eye - you see the object or the object larger. In the following graphic you can see the normal view of an object above, which is shown relatively small on the retina. Below, the magnifying glass creates a virtual image that is shown much larger on the retina.
The compound microscope
A microscope now consists of two parts: the objective creates a "real image" in the microscope, which is then further enlarged with the help of the eyepiece, which acts like a magnifying glass. This creates a typical beam path that is often used for the functionality of the microscope. The following figure illustrates the beam path in the microscope:
The following video illustrates the process:
The following stamp from 1968 illustrates the principle once again:
Books on microscopes / microscopy
The following list contains some products that can be ordered directly from Amazon. A click on the price opens the Amazon page (* partner link). Please note that the prices are without guarantee, as they can change at short notice.
|product||description||Price on Amazon *|
€ 9.99 (Amazon)
What's what? Microscope (volume 8)
€ 9.95 (Amazon)
The great cosmos book of microscopy
€ 39.99 (Amazon)
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