Brief history of light

The term LIGHT (Latin, lux, lucis) refers to the portion of the electromagnetic spectrum seen by the human eye, and is roughly between 400 and 700 nanometers in wavelength, or between 750 and 428 THz frequency. This period coincides with the region of maximum emission from the sun. The limits of the visible spectrum the human eye are not equal for all people, but vary subjectively and may extend to 380 nanometers, closer to the ultraviolet and infrared approaching 730 nanometers.

Light, like all electromagnetic waves interact with matter. The most common phenomena are observed:

• absorption
• transmission
• reflection
• the rigrazione
• diffraction

Although electromagnetism Classima light is represented as a wave, with the advent of quantum mechanics to early twentieth century we have to realize that this has other typical properties of particles and explain phenomena such as the Compton effect. In modern physics, light is described as composed of quanta of electromagnetic field are called photons.

What is light?

The world is made of matter and energy, two sources only apparently so different but related point that they can transform one into the conditions permitting. The UCE is part of the second category and is not material. What makes the light then? This is a very old question which answer is rather recent, a response that unfortunately is a bit ambiguous. That light is not material and it was apparent right away, what then can be transmitted over large distances without transport of matter?

Waves. The waves of the sea, those do sound and hence the light could behave the same way. Wave with its value of wavelength and frequency even better different values of wavelengths and frequencies. The phenomenon of disepersione of light through a prism, was analyzed by Isaac Newton in 1666, showed the coexistence of several wavelengths corresponding to its color, forced to separate as they pass through the prism. Newton was very tight between what was called the wave and particle theory that light was made of material particles that propagate in a straight line.

Wave-particle duality

This was the theory that convinced him maggiornamente and this made the focus of his studies which showed that the particles in passing through the prism of our national not be equal but deflected differently by providing different colors. The evidence of the propagation of light in a straight line was a clue to the existence of particles of light, but belied the phenomenon of diffraction in the light phenomena characteristic of waves.

The Dutchman Christiaan Huygens became the spokesman for teroia wave, carrying on a debate about the nature of light now known as wave-copuscolo duality of light. This was because of this duality to be found in the fact that the light seemed to behave like a wave and a particle depending of the experiments carried out without express simultaneously the two aspects.

The dualism of wave or particle did not resolve Another important issue to be resolved: what was the propagation medium, it seemed inconceivable to think the possibility of transmission in a vacuum, of course you knew that the light is transmitted in the absence of air but it was necessary to admit the existence of half material that allowed the spread. It should be a means not perceptible under common immaterial, evanescent, thin and transparent, and ether Aristotelian lent itself well to these characteristics.

Aristotle in fact, in his cosmology, admitted the existence of four terrestrial elements (earth, water, air and fire) and a fifth element celestial ether precisely. Aristotle imagine two different physical short, one for the earthly world and the other for the sky beyond the Moon (the Earth for Aristotle it was the center of the solar system).

Galileo and Einstein are clearly

Through the use of the telescope Galileo was able to break down the division between terrestrial and celestial physics showing mofologie and celestial dynamics similar to those existing on Earth.

Only Albert Einstein in the early twentieth century, however, allowed us to undermine the existence of the ether. The light can be Across the void and even send in a vacuum reaches its maximum speed (nearly 300,000 km / s) value, which the materials of Einstein's relativity, is unsurpassed.

It remains to solve the wave-particle duality.

Bohr's principle of complementarity

Einstein won the Nobel Prize in 1922 with the photoelectric effect that response in vogue corpuscle theory of light (as light or photon) after years of theory wave sembraba the most likely. Light shot on the metal behaved as a set of bullets of light, pointing to a non-continuous and discrete nature, a set of packets of light (massless) with energies differenti.Ovviamente could not ignore the phenomenon of diffraction and other evidence of the wave theory, the light thus had an ambivalent nature, sometimes represented as a wave (diffraction) sometimes as a particle (effect photoelectric).

Summarizing it is clear that light is wave and particle at the same time, nature does not exclude the other party will show at once. This was expressed by the complementarity principle of Bohr cossiddetta who founded the Copenhagen School of quantum physics.

So the dualism remains, is inherent in the light or maybe corpuscle and wave are two Eneti that man imagines to describe the properties of something whose true is another nature, a nature incomprehensible to humans. Indeed, quantum physics teaches us that nature has in itself the limit that prevents his intimate knowledge and its truth.

The man must think of not to know the essence of the thing, but only some of his behaviors, allowing you to make predictions in a probabilistic and not certain.