Light is a form of electromagnetic radiation whose frequency is visible to the human eye. Light can propagate in a vacuum with velocity of approximately 300 thousand km/s. The frequencies of light that are visible to the human eye are called visible spectrum, these waves have lengths between 400nm and 700nm.
Electromagnetic waves that have frequencies lower than visible light are called infra-red, while those with higher frequencies are called ultraviolet.
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Visible light has wavelengths between 400 nm and 700 nm.
Concept
Light has already been studied and interpreted in different ways, among some of its descriptions we can highlight the geometric, a undulatory and the corpuscular.
Geometric: Light can be represented by lines, commonly called light rays. A set of light rays, in turn, is called a beam. For geometric optics, light propagates only in straight line. The geometric interpretation of light is able to explain how lenses and mirrors work. To learn more about geometric optics, click on here.
Undulating: light is capable of propagate in space, carrying energy with you. The frequency of light, in this case, refers to the number of oscillations carried out by the electric and magnetic fields, each second. According to the wave nature, light propagates in a direction perpendicular to the electromagnetic field that originates it. The electromagnetic description of light also explains the emergence of the phenomena of interference,diffraction,refraction and polarization, for example. To learn more about waves, click on here.
Electromagnetic waves are formed by electric and magnetic fields.
Corpuscular: Light is formed by a large number of particles endowed with linear motion, although massless, calls from photons. This type of interpretation is also capable of explaining the aforementioned phenomena, as well as some quantum phenomena, such as the photoelectric effect.
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Nature
The nature of light concerns what it forms. Throughout the history of Physics, there have been scientists who defended the wave nature of light, such as Thomasyoung, while others defended its corpuscular nature, such as Isaac Newton. Currently, after contributions made by physicists MaxPlanck and Albert Einstein, it is understood that the nature of light is dual, that is: now she behaves as a wave, now how particle. This behavior, called "wave particle duality”, is also observed in other quantum particles, such as protons, neutrons and electrons.
Features
Among the characteristics of light, we can highlight some of the most important:
Intensity: Light intensity measures the amount of energy it radiates each second per unit area.
Frequency: The frequency of light measures how many oscillations it undergoes each second.
Polarization: Polarization is determined by the angle of vibration of the electric field that forms light.
Sources
Any body capable of emanate light can be considered a light source. there are light sources primaries and secondary.
Primaries: are capable of producing their own light, they are also called luminous bodies. Example: lit match, Sun, lit lamp.
Secondary: are capable of just reflecting the light that falls on them, they are also known as illuminated bodies. Example: illuminated wall, clouds, people.
issue
The light emitted by primary sources can be produced by different processes. We can classify the light emission processes into: luminescent and thermoluminescent.
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Thermoluminescence: is the emission of light due to thermal excitation. With heating, atoms get their electrons excited. In the relaxation process, these electrons emit light. Example: emissions from black body, like red-hot coals.
The light emitted by the burning coal is obtained by thermoluminescence. Luminescence: they are all light-emitting processes motivated by some kind of excitation other than thermal excitation. Among the luminescence processes, we can highlight photoluminescence (light emission after photon absorption), responsible for fluorescence and phosphorescence, bioluminescence etc.
Plankton emit light through bioluminescence.
See too: Understand the difference between fluorescent and phosphorescent
By Me. Rafael Helerbrock
