The physical term "spectrum" comes from the Latin word spectrum, which means "vision", or even "ghost".
But an object called such a gloomy word has a direct relation to such a beautiful phenomenon of nature as a rainbow.
In a broad sense, the spectrum is calledDistribution of the values of a certain physical quantity. A special case is the distribution of the frequencies of electromagnetic radiation. The light that is perceived by the human eye is also a kind of electromagnetic radiation, and it has a spectrum.
The honor of opening the spectrum of light belongs to I.Newton. Starting this research, the scientist pursued a practical goal: to improve the quality of lenses for telescopes. The problem was that the edges of the image, which could be observed in the telescope, were painted in all the colors of the rainbow.
AND.Newton put the experience: in a darkened room through a small hole penetrated a ray of light, which fell on the screen. But on his way was established a trihedral glass prism. On the screen instead of a white light spot, a rainbow strip was designated. White sunlight was complex, compound.
The scientist complicated the experience. He began to make small holes in the screen, so that only one colored beam (for example, red) passed through them, and a second prism and another screen was installed behind the screen. It turned out that the colored rays, on which the first prism spread out the light, do not decompose into their constituent parts, passing through the second prism, they only deviate. Consequently, these light rays are simple, and they are refracted in the prism in different ways, which allowed to "decompose" the light into parts.
So it became clear that different colors do not occurFrom different degrees of "mixing light with darkness," as was believed before I. Newton, but are components of the light itself. This composition was also called the spectrum of light.
The discovery of I.Newton was important for his time, it gave a lot to the study of the nature of light. But the true revolution in science, connected with the study of the spectrum of light, occurred in the middle of the XIX century.
German scientists R.V. Bunsen and G.R.Kirchhoff studied the spectrum of light emitted by fire, to which are mixed evaporation of various salts. The spectrum varied depending on impurities. This led researchers to the idea that the light spectra can be used to judge the chemical composition of the Sun and other stars. So the method of spectral analysis was born.
This discovery was important not only forPhysics, chemistry and astronomy, but also for philosophy - in the matter of knowledge of the world. At that time, many philosophers believed that in the world there are phenomena that a person can not fully comprehend until the end. As an example, the Sun and stars that can be observed, you can calculate their mass, size, distance to them, but you can not study their chemical composition. With the advent of spectral analysis, this characterization of stars ceased to be unknowable, which means that the very idea of the unknowability of the world was questioned.