Introduction
We continue with the wonderful analysis of our electromagnetic spectrum, and to do so we will use fundamental principles of geometric optics and its conceptualization of light ray whose propagation is rectilinear, and of course having as reference the spectral fraction of our white or visible light because through it we have been able to obtain essential knowledge for our development and welfare.
Our surroundings emit innumerable luminous rays as much perceptible as imperceptible for our natural optical systems as they are our eyes, with the perceptible rays we can generate any type of images in our retinas when being refracted by our natural lenses like the cornea and the crystalline one, and in addition these images also are possible to capture them through any type of artificial optical instrument designed by the man through its nourished scientific-technological history, between these optical instruments we can emphasize to the well-known cameras, among others, which will be analyzed in future articles.
We have started from our visible light, where, we could elaborate in a homemade way a wonderful optical instrument called spectroscope and by means of the same one we managed to decompose to the white light in its different component colors and this way it was managed to verify that each dispersed color is represented by different wavelengths, since this causes that each wavelength according to the spectrum of our visible light.
In the previous delivery we analyzed generally to the infrared rays and thus we entered to know those luminous rays imperceptible to our eyes, nevertheless, these invisible rays to our glance have great influence in any activity of our daily life as they could notice it with the infrared rays and their applications, between which it is in our control or remote control implemented for the ignition or extinction of any household-electric in our houses or work place.
In this opportunity we will jump to the other side of our referential spectral fraction, that is to say, to the left side of the white or visible light, and where we will find according to our composition of the electromagnetic spectrum the ultraviolet light (UV) and the same as the infrared rays are imperceptible to our natural optical systems (eyes), however, the same are implemented in some of our activities.
We know that our splendid central star, the Sun, transmits to us its marvelous energy, and we have classified it in relation to a wide wavelength scale, where those with the longest wavelengths belong to the radio waves, microwaves, and as for the shortest wavelengths, they belong to that part of the electromagnetic spectrum reserved for ultraviolet rays, the known X-rays and gamma rays.
My friends, it is necessary to be able to emphasize that thanks to the spectrum of our white or visible light, we can identify the range of the infrared because it is below the red one, and in the same way we locate the important spectrum of the ultraviolet rays, because this last one we obtain after the violet color and from there that they are ultraviolet.
When we refer to ultraviolet light, we are referring to certain rays belonging to the great family of rays that are not in the spectrum visible to the human eye, however, thanks to science and technology have been able to design extraordinary optical instruments such as lamps with special materials that can transform UV rays into visible wavelengths, and also implement them in a favorable way in countless and important activities within humanity.
It is important to mention that in this opportunity we will experiment or look for the way to try to visualize these ultraviolet rays by means of the adaptation of an element (translucent) to a white light lantern, this will represent a simple but wonderful experiment that will allow us to make the similarity of some things that the true ultraviolet lamps make.
Ultraviolet rays
It is always necessary to emphasize the aspect that allows us to express that the light from the point of view of the physical optics, is a wonderful phenomenon in the form of electromagnetic radiation, and to the same one we can call it radiant energy, and in addition, we have expressed that this energy propagates or moves in form of waves in any type of means (as much material or in the emptiness) and as we indicated previously with a direction established by the geometric optics, that is to say, with a rectilinear propagation.
Despite the fact that we cannot see ultraviolet rays, however, if we could detect their action on our skin, this being for a long interval of time exposed to them, generally, would cause us a sensation of heat and we would also notice how our skin changes color to what we commonly call tan, as we can visualize in the following figure 1.
Figure 1. Ultraviolet rays emitted by the Sun, impacting our skin
The previous figure 1, represents a daily example of how to get a tan and at the same time receive energy from the different luminous rays or radiations of the Sun's light, especially ultraviolet rays, this exposure to the Sun must be moderate, since it is more than demonstrated that an excess of exposure could bring serious consequences to our skin such as burns, wrinkles, aging and also serious problems such as skin cancer, among others.
It is important to emphasize that ultraviolet rays are very useful for humanity, and despite being imperceptible to our natural optical instruments (eyes), man through science has been able to take it to wavelengths captured by the human eye, but it is always important to note that we must control the amount of emission of these rays to our skin.
Ultraviolet ray spectrum (UV)
As described above, ultraviolet light is part of the large family of electromagnetic radiation, this makes it transfer energy from one part of the universe to another, these rays like the other electromagnetic spectral fractions are measured in wavelengths and whose propagation is rectilinear.
It is important to point out that the spectrum visible by the human eye radiates or shines between the interval of 400 and 700 nanometers (nm), when referring to the ultraviolet rays its interval is between 10 and 400 nm, where the region that represents the spectrum of ultraviolet light can be divided into four sub-regions as we can observe in the following figure 2.
Figure 2. Regions of the UV light spectrum
*The UVA sub-region, also called long wave UV, radiates in the 320-400 nm range.
*The UVB sub-region can also be called medium wave length UV and ranges from 280 nm to 320 nm.
*The UVC sub-region, also known as short wavelength UV, ranges from 180 to 280 nm.
*The UV vacuum sub-region is located between 10 and 180 nm, this type of light can only remain in the vacuum as it would otherwise be quickly absorbed by the air.
It is important to emphasize the great utility that this type of UV light has in our activities, we can express that any visible light will carry an ultraviolet light radiation during the emission of its rays, however, we could ask ourselves the following question:
¿It is possible that through some home method we can visualize the action of this type of ultraviolet light?
We will answer this interesting question when doing our little home experiment and we will also make some demonstrations with the filtered rays of white light emitted by an artificial source such as a flashlight, we will use some materials easily accessible in our homes as you can see in the following figures that show the most essential steps in such an experiment.
Once our home experience with the purpose of generating ultraviolet light has been carried out, we need to know if this generation of home UV light really works, therefore, let's make some examples and thus verify if we have really achieved our purpose.
Many of us have noticed that the ultraviolet rays have diverse applications, therefore, we will carry out some of them with our homemade UV light, and in this way, we will verify its action in the authentication of the paper money implemented in our bills, where, it is important to emphasize that they carry certain hidden marks that only through UV light we can observe, among other examples, are the detection of some trace of urine, saliva or blood, next we observe the application of our UV light in the following figure 3.
Figure 3. Using our homemade UV light to detect any trace or mark not visible to our eyes and know if it works or not?
In the previous examples we were able to verify that our homemade UV light did not fulfill the purpose entrusted to it, we were able to observe that it strengthens any type of writing with some type of fluorescent marker (c), but in the examples (a) and (b) we could not visualize traces or prints invisible to our eyes.
To achieve this purpose, it is necessary to have optimal conditions and adequate materials for the crystals implemented in the manufacture of lamps that emit ultraviolet rays, among which we find the lamps with Wood's crystal filters, which are structured by chemical elements such as barium-sodium silicate and nickel oxide, components that would be difficult to find in our homes.
With this experience we achieved the similarity of UV light and the same is implemented both in the above examples as in others, since some lengths of these UV rays are able to neutralize some microorganisms which make them germicides.
Conclusion
We continue with the conformation of our essential electromagnetic spectrum, where, we have already analyzed our referential spectral fraction as it is the white or visible light, from this reference we begin to know the other component fractions of this electromagnetic spectrum and the same as we have expressed are imperceptible to our natural optical systems (eyes).
In this way we already analyze the infrared rays whose wavelength is greater than that of white light and in this way its frequency is less than that of our reference fraction, in this opportunity we jump to the other side of the white light spectrum and we find the rays or ultraviolet light, whose wavelength is less than that of white light and in this way its frequency is greater.
We made a small but significant practical experience with the purpose of trying to generate UV light at home, however, despite achieving a certain amount of the spectrum of white light similar to UV light we did not achieve our purpose, since to achieve UV light is necessary to have special materials for the manufacture of glass filters with which instruments or devices are made to obtain UV light.
We can find many applications of UV light, to name but one example we have, the fluorescence visible through the radiation of the same, due to this, these rays allow us to find some hidden fingerprint on some object as is the case of paper money for the development of the various bills of each country, and thus check if these bills are counterfeit or not.
Another important application is the visualization of other hidden fingerprints for our view as in personal documents such as passports, fingerprints, or those prints originated by blood on certain surfaces and that at first sight is not possible to observe, these are some examples but there are other important applications of ultraviolet.
Until another delivery my appreciated readers of Hive.blog, specially to the members of the great community of #Stemsocial, which receives the support of another wonderful community like #curie, reason why I recommend widely to be part of this exemplary project, since they allow us to emphasize the wonderful task of the academy and the enormous work of all the scientific field.
Note: All the images were elaborated using the Power Point application and the animated gif was elaborated with the PhotoScape application, the photostatic images were captured by the optical instrument (camera) of the ZTE BLU Life Play 2 cell phone.