- Tutorial
Friends, Friday evening is approaching, this is a wonderful intimate time when, under the cover of an alluring twilight, you can take out your spectrometer and measure the spectrum of an incandescent lamp all night, until the first rays of the rising sun, and when the sun rises, measure its spectrum.
How come you still don't have your own spectrometer? It doesn’t matter, let’s go under the cut and correct this misunderstanding.
Attention! This article does not pretend to be a full-fledged tutorial, but perhaps within 20 minutes of reading it you will have decomposed your first radiation spectrum.
Man and spectroscope
I will tell you in the order in which I went through all the stages myself, one might say from worst to best. If someone is immediately focused on a more or less serious result, then half of the article can be safely skipped. Well, people with crooked hands (like me) and simply curious people will be interested in reading about my ordeals from the very beginning.There is a sufficient amount of material floating around on the Internet on how to assemble a spectrometer/spectroscope with your own hands from scrap materials.
In order to acquire a spectroscope at home, in the simplest case you will not need much at all - a CD/DVD blank and a box.
My first experiments in studying the spectrum were inspired by this material - Spectroscopy
Actually, thanks to the author’s work, I assembled my first spectroscope from a transmission diffraction grating of a DVD disc and a cardboard tea box, and even earlier, a thick piece of cardboard with a slot and a transmission grating from a DVD disc was enough for me.
I can’t say that the results were stunning, but it was quite possible to obtain the first spectra; photographs of the process were miraculously saved under the spoiler
Photos of spectroscopes and spectrum
The very first option with a piece of cardboard 
Second option with a tea box 
And the captured spectrum
The only thing for my convenience, he modified this design USB video camera, it turned out like this:
photo of the spectrometer
I’ll say right away that this modification saved me from having to use the camera mobile phone, but there was one drawback: the camera could not be calibrated to the settings of the Spectral Workbench service (which will be discussed below). Therefore, I was not able to capture the spectrum in real time, but it was quite possible to recognize already collected photographs.
So let's say you bought or assembled a spectroscope according to the instructions above.
After this, create an account in the PublicLab.org project and go to the SpectralWorkbench.org service page. Next, I will describe to you the spectrum recognition technique that I used myself.
First, we will need to calibrate our spectrometer. To do this, you will need to get a snapshot of the spectrum of a fluorescent lamp, preferably a large ceiling lamp, but an energy-saving lamp will also do.
1) Click the Capture spectra button
2) Upload Image
3) Fill in the fields, select the file, select new calibration, select the device (you can choose a mini spectroscope or just custom), select whether your spectrum is vertical or horizontal, so that it is clear that the spectra in the screenshot of the previous program are horizontal
4) A window with graphs will open.
5) Check how your spectrum is rotated. There should be a blue range on the left, red on the right. If this is not the case, select the more tools – flip horizontally button, after which we see that the image has rotated but the graph has not, so click more tools – re-extract from foto, all peaks again correspond to real peaks.
6) Press the Calibrate button, press begin, select the blue peak directly on the graph (see screenshot), press LMB and the pop-up window opens again, now we need to press finish and select the outermost green peak, after which the page will refresh and we will get a calibrated wavelengths image.
Now you can fill in other spectra under study; when requesting calibration, you need to indicate the graph that we have already calibrated earlier.
Screenshot
Type of configured program 
Attention! Calibration assumes that you will subsequently take photographs with the same device that you calibrated. Changing the resolution of the images in the device, a strong shift in the spectrum in the photo relative to the position in the calibrated example can distort the measurement results.
Honestly, I edited my pictures a little in the editor. If there was light somewhere, I darkened the surroundings, sometimes rotated the spectrum a little to get a rectangular image, but once again, it is better not to change the file size and the location relative to the center of the image of the spectrum itself.
I suggest you figure out the remaining functions like macros, auto or manual brightness adjustment yourself; in my opinion, they are not so critical.
It is then convenient to transfer the resulting graphs to CSV, in which the first number will be a fractional (probably fractional) wavelength, and separated by a comma will be the average relative value of the radiation intensity. The obtained values look beautiful in the form of graphs, built for example in Scilab
SpectralWorkbench.org has apps for smartphones. I didn't use them. so I can't rate it.
Have a colorful day in all the colors of the rainbow, friends.
SPREAD OF LIGHT
Take three postcards and use scissors to cut a hole the size of a penny in the middle of each card. Make a stand for each card from lumps of plasticine and stick them on the table in a line so that the holes are in one straight line.
Shine a flashlight into the hole of the card that is furthest from you, and look through the hole of the nearest card.
What do you see? What about the path that light takes from a flashlight to your eye?
Move the middle card a couple of centimeters to the side so that it now blocks the path of light. What do you see now? What happened to the light? Can you see any traces of light on the card that is pulled back?
Light travels in a straight line. When all three holes are on the same line, the light spreads from the flashlight along this line and hits your eyes;
When the middle card is shifted, an obstacle appears in the path of the light, and the light cannot go around it, since it travels in a straight line. The card prevents it from going the rest of the way to your eye.
OBTAINING SPECTRUM
There is actually more to the color white than meets the eye. It is a mixture of all the colors of the rainbow - red, orange, yellow, green, blue, indigo and violet. These colors make up what is called the visible spectrum. There are several ways to separate white light into its components. Here's one of them.
Fill a bowl with water and place it on a well-lit surface. Place a mirror inside and tilt it so that it rests on one of the sides of the cuvette.
Look at the reflection that the mirror casts on a nearby surface. What do you see? To make the image clearer, place a sheet of white paper in the place where the reflection is cast.
Light travels in waves. Like sea waves, they have crests called maxima and troughs called minima. The distance from one maximum to another is called the wavelength.
A beam of white light contains rays of light with different wavelengths. Each wavelength corresponds to a specific color. V red has the longest wavelengths. Next come orange, then yellow, green, blue and blue. Violet has the shortest wavelengths.
When white light is reflected in a mirror through water, it is broken down into its component colors. They diverge and form a pattern of parallel stripes of color called a spectrum.
And look at the surface of the CD. Where did the rainbow come from here?
SPECTRUM ON THE CEILING
Fill the glass one-third full with water. Place the books in a stack on some smooth surface. The stack should be slightly higher than the length of the flashlight.
Place the glass on top of a stack of books so that part of it extends slightly beyond the edge of the book and hangs in the air, but the glass does not fall.
Place the flashlight under the hanging part of the glass almost vertically, and secure it in this position with a piece of plasticine so that it does not slip. Turn on the flashlight and turn off the lights in the room.
Look at the ceiling. What do you see?
Repeat the experiment, but now fill the glass two-thirds full. How has the rainbow changed?
The beam of a flashlight falls on a glass filled with water at a slight angle. As a result, white light is decomposed into its constituent components. Colors adjacent to each other continue their path along diverging trajectories and, eventually ending up on the ceiling, give such a wonderful spectrum.
1.What does a continuous spectrum look like? What bodies produce a continuous spectrum? Give examples.
A continuous spectrum is a strip consisting of all the colors of the rainbow, smoothly transitioning into each other.
A continuous spectrum is obtained from the light of solid and liquid bodies (the filament of an electric lamp, molten metal, a candle flame), with a temperature of several thousand degrees Celsius. It is also produced by luminous gases and vapors at high pressure.
2. What they look like line spectra? What light sources produce line spectra?
Line spectra consist of individual lines of specific colors.
Line spectra are characteristic of luminous gases of low density.
3. How can a line emission spectrum of sodium be obtained?
To do this, you need to pass light from an incandescent lamp through a vessel with sodium vapor. As a result, narrow black lines will appear in the continuous spectrum of light from an incandescent lamp, in the place where the yellow lines are located in the sodium emission spectrum.
4. Describe the mechanism for obtaining line absorption spectra.
Line absorption spectra are obtained by passing light from a brighter and hotter source through low-density gases.
5. What is the essence of Kirchhoff’s law regarding line emission and absorption spectra?
Kirchoff's law states that atoms of a given element absorb and emit light waves at the same frequencies.
6. What is spectral analysis and how is it carried out?
The method of determining the chemical composition of a substance from its line spectrum is called spectral analysis.
The substance under study in the form of a powder or aerosol is placed in a high-temperature light source - a flame or an electric discharge, due to which it becomes an atomic gas and its atoms are excited, which emit or absorb electromagnetic radiation in a strictly defined frequency range. The photograph of the spectrum of atoms obtained using a spectrograph is then analyzed.
By the location of the lines in the spectrum, they know what elements a given substance consists of.
By comparing the relative intensities of the spectrum lines, the quantitative content of elements is estimated.
7. Explain the application of spectral analysis.
Spectral analysis is used in metallurgy, mechanical engineering, the nuclear industry, geology, archeology, forensics and other fields. The use of spectral analysis in astronomy is especially interesting; it is used to determine the chemical composition of stars and planetary atmospheres, and their temperature. Based on the shifts of the spectral lines of galaxies, they learned to determine their speed.
The great English scientist Isaac Newton used the word “spectrum” to designate the multi-colored band that is obtained when a solar ray passes through a triangular prism. This band is very similar to a rainbow, and it is this band that is most often called the spectrum in everyday life. Meanwhile, each substance has its own emission or absorption spectrum, and they can be observed if several experiments are carried out. The properties of substances to produce different spectra are widely used in various fields of activity. For example, spectral analysis is one of the most accurate forensic methods. Very often this method is used in medicine.
You will need
- - spectroscope;
- - gas-burner;
- - a small ceramic or porcelain spoon;
- - pure table salt;
- - a transparent test tube filled with carbon dioxide;
- - powerful incandescent lamp;
- - powerful “economical” gas light lamp.
Instructions
- For a diffraction spectroscope, take a CD, a small cardboard box, or a cardboard thermometer case. Cut a piece of disk to the size of the box. On the top plane of the box, next to its short wall, place the eyepiece at an angle of approximately 135° to the surface. The eyepiece is a piece of a thermometer case. Select the location for the gap experimentally, alternately piercing and sealing holes on another short wall.
- Place a powerful incandescent lamp opposite the spectroscope slit. In the spectroscope eyepiece you will see a continuous spectrum. Such a spectral composition of radiation exists for any heated object. There are no emission or absorption lines. In nature, this spectrum is known as a rainbow.
- Place salt in a small ceramic or porcelain spoon. Point the spectroscope slit at a dark, non-luminous area located above the light burner flame. Add a spoonful of salt into the flame. At the moment when the flame becomes intensely colored yellow, in the spectroscope it will be possible to observe the emission spectrum of the salt under study (sodium chloride), where the emission line in the yellow region will be especially clearly visible. The same experiment can be carried out with potassium chloride, copper salts, tungsten salts, and so on. This is what emission spectra look like - light lines in certain areas of a dark background.
- Point the working slit of the spectroscope at a bright incandescent lamp. Place a transparent test tube filled with carbon dioxide so that it covers the working slit of the spectroscope. Through the eyepiece, a continuous spectrum can be observed, intersected by dark vertical lines. This is the so-called absorption spectrum, in this case of carbon dioxide.
- Point the working slit of the spectroscope at the switched on “economical” lamp. Instead of the usual continuous spectrum, you will see a series of vertical lines located in different parts and having mostly different colors. From this we can conclude that the emission spectrum of such a lamp is very different from the spectrum of a conventional incandescent lamp, which is imperceptible to the eye, but affects the photography process.
The type of spectra of luminous gases depends on chemical nature gas
Emission spectrum
Question 5. Emission spectra. Absorption spectra
Question 4: Application of variance
The phenomenon of dispersion underlies the design of prism spectral instruments: spectroscopes and spectrographs, which are used to obtain and observe spectra. The path of rays in the simplest spectrograph is shown in Fig. 4.
A slit illuminated by a light source, placed at the focus of a collimator lens, sends a beam of divergent rays to this lens, which the lens (collimator lens) turns into a beam of parallel rays.
These parallel rays, refracted in a prism, split into rays of light of different colors (i.e., different), which are collected by a camera lens (camera lens) in its focal plane and instead of one image of the slit, a whole series of images is obtained. Each frequency has its own image. The combination of these images represents the spectrum. The spectrum can be observed through an eyepiece used as a magnifying glass. Such a device is called spectroscope. If you need to take a photograph of a spectrum, then the photographic plate is placed in the focal plane of the camera lens. A device for photographing a spectrum is called spectrograph.
If the light from the red-hot solid pass through the prism, then on the screen behind the prism we get continuous continuous emission spectrum.
If the light source is gas or vapor, then the spectrum pattern changes significantly. A collection of bright lines separated by dark spaces is observed. Such spectra are called ruled. Examples of line spectra are the spectra of sodium, hydrogen and helium.
Each gas or vapor produces its own characteristic spectrum. Therefore, the spectrum of the luminous gas allows us to draw a conclusion about its chemical composition. If the radiation source is molecules of matter, then a striped spectrum is observed.
All three types of spectra - continuous, line and striped - are spectra emissions.
In addition to emission spectra, there are absorption spectra, which are obtained as follows.
White light from the source is passed through the vapor of the substance under study and directed to a spectroscope or other device designed to study the spectrum.
In this case, dark lines arranged in a certain order are visible against the background of a continuous spectrum. Their number and arrangement make it possible to judge the composition of the substance under study.
For example, if sodium vapor is in the path of the rays, a dark band appears on the continuous spectrum in the place in the spectrum where the yellow line of the sodium vapor emission spectrum should have been located.
The phenomenon under consideration was explained by Kirchhoff, who showed that the atoms of a given element absorb the same light waves that they themselves emit.
To explain the origin of the spectra, it is necessary to know the structure of the atom. These issues will be discussed in further lectures.
Literature:
1. I.I. Narkevich et al. Physics. - Minsk: Publishing House “New Knowledge LLC”, 2004.
2. R.I. Grabovsky. Physics course. - St. Petersburg - M. - Krasnodar: Lan Publishing House, 2006.
3. V.F.Dmitrieva. Physics.- M.: Publishing house “ graduate School”, 2001.
4. A.N.Remizov. Course of physics, electronics and cybernetics. - M.: Publishing house “Higher School”, 1982
5. L.A. Aksenovich, N.N. Rakina. Physics. - Minsk: Publishing House “Design PRO”, 2001.
