Science has a whole branch to explain how do light microscopes work. A simple microscope contains a lens with high magnification, also known as a loupe. The multiple lenses in the compound microscope aim to enlarge the image without reducing the resolution and chromatic aberration. Even specialized microscopes like electron microscopes are based on the same concept as their counterparts, even though they might operate differently.
Build of an Optical Microscope
It is necessary to look at all the components comprising an optical microscope to understand its working correctly. Typically, a microscope contains some lenses in a container to magnify the image using basic optical principles. It might have some other components to improve the image quality and to prevent the details.
The Lenses
The most integral part of a microscope is the lenses. Whenever we are talking about the magnification power of a microscope, we are talking about its lenses. A compound microscope consists of two or more lenses. One lense is called the eyepiece that sits at the top of the tube body. Some microscopes are binocular and contain two eyepiece lenses.
In the microscopes, three or four object lenses reside in a revolving turret; this helps make the magnification variable. The magnification can be varied by turning the turret; this lines up a different objective lens in front of the body tube, which changes the magnification power. The objective lens is normally found closest to the object at the bottom of the microscope.
The Stage
The Scene On a surface known as the microscope’s stage, the object is placed immediately beneath the objective lens. The object is held in position on the stage by clips that slide in place for stable viewing. The microscopes also contain a mechanical stage that allows the object’s movement in a 2D direction or X and Y direction, and there are markers to note the location of the object. There is an aperture in the stage that allows the light to pass through and enlighten the object.
The Light
The light emission and light distribution are controlled by a diaphragm, condenser, and light source. They are located at the bottom of the stage. The illumination source is located at the bottom of the optical train. In simple microscopes, any form of light can be used as a light source which is then collected by a small mirror and reflected upwards into the aperture.
The illumination source type affects the sophistication of the microscope as its complexity increase. Different illumination sources provide various types of viewing benefits by meeting specific viewing requirements like Tungsten-halogen, mercury, metal halide lamps, and LEDs.
Working of Microscope – Optical
Optical is the crucial part of a microscope as three things are expected from a microscope: It must show a magnified image of the object being viewed, retain all its details, and make those details visible.
It is essential to understand these ideas to learn how a microscope work. The compound microscopes use visible light and two or more lenses. The light passes through the eyepiece towards the objective lens and then the object. When the object is placed within the lens’s focus, a magnified, virtual, and erect image is observed, which is a fundamental scientific principle.
Working of Microscope – Magnification
The power of the microscope or simply a lens to enlarge the image of the object is called its magnification. It depends upon both the lenses as the magnification is equal to Mo x Me. The magnification of an objective lens is Mo which is determined by the focal length of the lens and the distance between the object focal plane and the eyepiece focal plane. Whereas Me is the eyepiece’s magnification, and it also depends upon the eyepiece’s focal length.
Working of Microscope – Resolution
In the microscope world, resolution means the ability of the microscope to distinguish the details of the object. Resolution is a crucial feature of a microscope. It may have more value than magnification because if the image of the object cannot be seen clearly, then no matter how much the magnification is, it will be of no use.
The resolution depends upon the refractive index of the medium and the angular aperture, but these attributes don’t just rely on the lens. Instead, the whole system is taken into account. Also, the wavelength of the light is very important for the resolution because the shorter the wavelength is, the better the resolution will be.
The measure of resolution in microscopes is in microns; a good microscope can produce up to 0.2 microns or 200 nanometers of resolution. The smaller the micron value, the greater the result, e.g., a microscope with 0.5-micron resolution can not resolve points with a distance of 0.3 microns between them.
Working of Microscope – Contrast
A good contrast has as much significance as the resolution and magnification. Because if all of the light is reflected or observed by the object, you won’t be able to see the image, some frequencies of light must be absorbed, and some must be reflected to see the image.
The size and intensity of the light beam can be adjusted using the condense and the diaphragm. The narrow the beam would be, the higher the contrast will be. It might become necessary to stain the object to obtain a certain contrast level to make the object more visible.
Working of Microscope – Electron
In electron microscopes, the electron guns fire a beam of electrons with a shorter wavelength than visible light. Because of this, the electron microscope has high resolution and magnifications. An electron microscope also works in the same way as a simple microscope to some extend. The difference is that the electron microscope uses a beam of electrons rather than using the visible length to illuminate the object. The beam of the electron is focused using magnetic lenses. The image is formed by looking at the changes in the electron beam inside the image, which is then recorded to create the image.
Conclusion
The working of a microscope is very simple but, at the same time, very complicated. It combines many different factors, and a good microscope must have a good resolution, magnification, contrast, and brightness. The best microscopes in the world can produce a resolution of up to a few nanometers, which are highly incredible.