[Evolution Concept of Light] The nature of light is much discussed. The two theories in the past were more disputes the primacy of truth had been indisputable that wave and particle theory. The first was formulated in the early seventeenth century by English physicist Isaac Newton. The thesis set out the principles according to which light is nothing more than an aggregate of particles of different species (this was to explain the wide range of colors) at a constant rate projected by luminaries better not be specified. At the time there were those who considered it a mere restatement of the ancient Greek theory of atoms. Surely shoot some considerations, but this did not lead to discredit it. The second was formulated in the mid-seventeenth century by the Dutch physicist Christiaan Huygens. The scientist found that, like the sound, the light was a phenomenon due to the incessant vibration of the ether cosmico.Inizialmente the corpuscular theory gained greater consensus, not because of his infallibility, as to the fallibility of the litigant, whose wave mechanics had not yet been well explained. However, at the dawn of the nineteenth century, the principles theorized by the English physicist Thomas Young and the French physicist Augustin-Jean Fresnel, the wave theory surclasserà by far the particle. Although the claims made by the two physicists explain, both from a quantitative and qualitative terms, the totality of the phenomena light known at the time, still lacked the fundamentals of mechanics of the weaknesses are not negligible. The ether was still considered it as a thin and fluid, given the thesis about the mode of propagation of light, this would contradict the principles of interference (explained by observing the light of the stars) and undermined the foundations of the ricerche.Fu British physicist James Clerk Maxwell to introduce mid-nineteenth century, the hypothesis of the electromagnetic nature of light, replacing the previous mechanical thesis. After the death of Maxwell's theories were taken and proven by the German physicist Heinrich Rudolf Hertz, who was able to generate, as predicted by Maxwell, to the point Behaviorally the same as light, through the use of a generator of electromagnetic waves. The theory of Maxwell and Hertz's experiments were investigated, and further revolutionized by the research carried out by the Dutch physicist Pieter Zeeman on the effects of magnetism on radiation (Zeeman effect) and the Nobel Prize in physics connaizonale Hendrick Antoon Lorentz, whose theory Electronic field would explain how the electromagnetic phenomena depend solely on the behavior of electrons. The next quantum theory, initiated by the inconsistencies between the concept of contiguity in the nature of the electromagnetic wave with the issue of the black and the photoelectric effect, he thought the light as an aggregate of individual units, known as photons. The energy of these particles was quantified by the formula:
E = hn, where n = frequency of the radiation, h = Planck's constant.
was precisely because of the constant introduction of Karl Max Plank began to emerge that the first case of modern quantum physics. [+ Wave-corpuscular?] From this we may deduce that the meeting between particle and wave theory, as might intuitively seem, will never be plausible according to the strictly literal sense of the concept of particles and waves. A photon, also called "quantum of light" or "quantum of energy" is not in fact a real particle, but rather an indivisible amount of electromagnetic energy. You must also think of the waves, not as an actual wave motion, but simply as a conceptual tool for determining the "fall" of photons on a body.
[Clarification of the Concept of Wave]
To better understand the concept of a wave, we now consider a wave mechanics. The basic features of a wave are:
length (lambda) is the distance in m (with multiple sub) between a ridge and the other
wave amplitude (A): that is, the distance between the highest point of the crest and the axis of wave propagation
frequency (ni): that the number of waves per unit of time (usually a second). It is expressed in Hertz (Hz, with multiple sub)
propagation speed (c) obviously assumes different values \u200b\u200bdepending on the type of wave. Taking into account the wave of the "bundle" of photons we have c = 300,000 km / s.
We can now derive the expressions that determine the direct and inverse relationships between the parameters above:
lambda = c / ni
ni = c / lambda
[The Blind Man is]
We then say us that men are able to perceive only a fraction of the totality of existing radiation which make up the solar electromagnetic spectrum. This fraction is called the visible spectrum. This means that our senses can perceive only radiation with frequencies and wavelengths. To get more specifically those frequencies ranging from 7.5 to 10 Hz at the 14th of violet to 4.3 Hz for 10 to 14th of red. To speak in terms of wavelength that we consider a spectrum of violet goes from 400nm to 700nm of rosso.Al above the visible spectrum (ie at higher frequencies) are ultraviolet, X-rays and finally, with the higher frequency of all the gamma rays. Below the visible spectrum and instead we find the infrared, with gradually diminishing frequency, la moltitudine di microonde che già in parte conosciamo.
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