Perhaps you have heard about the special electromagnetic waves perceived by the human eye, occupying a certain area of spectrum and having a wavelength of 380 nm (for violet) to 780 nm (for red).This is the visible radiation.Properties it is usually indicated in terahertz, we can find out by measuring the frequency response of such waves (we get a gap in the 400-790 THz).Visible light is also called visible light.To put it more simply, it is the light to which we are accustomed, and the physical side of which do not even think.The most sensitive indicator of our eye to the 555 nm (green part of the spectrum is the 540 THz).
interesting fact: in the spectrum does not contain some of the colors perceived by us.For example, there is no pink color (and colors).It is formed when mixing other colors.
Have you ever wondered why the sky looks blue?Quite simply part of the spectrum with shorter wavelengths is scattered more air than a length corresponding to the red side of the spectrum.Due to this the sky is blue, especially in the midday time.Visible radiation enters the so-called "optical window".This region of the spectrum the earth's atmosphere does not absorb.
Some animals can see light, inaccessible to human vision (it simply is not part of our visible range).Many insects (eg, bees) perceive the ultraviolet range, so they quickly find nectar in flowers.Ultraviolet radiation and are able to see the birds.Some species of birds even have labels that are visible only in the form of radiation, in which male and female accurately determine each other.
found visible radiation use in humans.The most widespread of its kind - the heat, based on the motion of atoms: the more heated body, the faster the movement of atoms that emit light in a collision.All our usual sources of light - the sun, incandescent, candle (flame) - are the thermal sources of visible light.
following example - electroluminescence.Here the energy is the cause of light emission, the atoms are obtained from non-thermal sources.When gas discharge an electric field is reported some kinetic energy of the electrons impinge on the atoms (the term "collide"), and the energy of the excited atoms we see in the form of luminescence (EL).
electroluminescence is now used for advertising luminous inscriptions.By the way, the aurora borealis also refers to the appearance of EL: streams of charged particles emitted by the Sun are attracted by the magnetic field of our planet, are excited at its poles and light.But CRTs in TV light thanks cathodoluminescence: glow here is bombardment by electrons.
Chemiluminescence - another example of visible light.Here the result of the glow becomes the energy released in chemical reactions.The temperature of the light source equal to the temperature of the medium in which it is located.An example could serve as a firefly with a small glowing green "flashlight".Light and other organisms: some fish, bacteria and insects.Sometimes you can see the glow of rotting trees.
Some bodies begin to glow after being exposed to light: absorbing the energy, they have themselves become sources of light.It - photoluminescence properties of which are widely used in paints, clothing, road signs and so on.
color components of visible light is used in the practice of psychology: Green is known to soothe red - excites, purple, black and blue - on the contrary, inhibitand even oppressed, and with a shortage of white color in humans and depression do occur.Visible radiation is used in medicine (chromotherapy): for example, yellow light is used in the treatment of certain eye diseases.Red light cured some diseases and pathology of sexual glands: infantilism, infertility, menstrual disorders in women, the number of seed failure in men, the extinction of sexual desire.Blue light eliminates itching, treat exudative diathesis and various types of bleeding.