In the 17th century there were two theories (wave and particle) that is light.According to the first, light is an electromagnetic wave.This was confirmed by the Maxwell equations, compiled in the 19th century.She is a very good description of the electrical and magnetic fields.Until now nobody has been able to prove that Maxwell's theory is wrong.
In the 20th century showed some phenomena that run counter to the views in the light wave.They include the photoelectric effect - the ejection of electrons from a substance incident light.According to the wave theory, this phenomenon should be a considerable delay: the light wave must pass a significant amount of energy to an electron so that it flew out of the matter.However, experiments have shown that there is practically no delay.Has created a new theory
, which states that the light - a stream of particles (corpuscles).Thus it was shown wave-particle duality of light.
wave properties of light
Phenomena confirming that light - electromagnetic wave is interference, diffraction and others.They are often used in various scientific studies.
interference - a superposition of two waves, resulting in an increase or decrease in the intensity of the radiation.The result is an interference pattern: alternating highs and lows, the highs have a radiation intensity 4 times higher than the intensity of the source.To observe the interference is necessary to have coherent sources (ie have the same frequency of the radiation and the constant phase difference).
corpuscular properties of light
Light reveals its corpuscular properties of the photoelectric effect.This phenomenon was discovered by the German physicist H. Hertz and experimentally investigated the Russian scientist AGStoletov.He's got some interesting data.The maximum kinetic energy of the emitted electrons depends on the frequency of the incident radiation.This is contrary to the concepts of classical physics.
For each substance there is a photoelectric threshold - the minimum frequency at which this phenomenon has been observed.Thus, the photoelectric effect can take place even at low incident radiation energy (the main thing that was a suitable frequency).An interesting finding was the fact that the number of electrons emitted from the surface of the substance per unit time, depends only on the intensity of the radiation (direct correlation).