Light is considered to be any kind of optical radiation.In other words, this electromagnetic wave, the length of which is in the range of several nanometers.
General Definitions
terms of optics, the light - is electromagnetic radiation that is perceived by the human eye.The unit changes made to take the land in a vacuum of 750 THz.It is the short-end of the spectrum.Its length is 400 nm.With regard to the border broad waves, the unit of measurement is taken of land in 760 nm, ie 390 THz.
In physics, light is regarded as a set of directional particles called photons.Speed wave distribution in vacuo constant.Photons possess a definite momentum, energy, zero mass.In a broader sense, the light - the visible ultraviolet radiation.Also, the waves can be infrakrasnymi.S the point of view of ontology, the light - this is the beginning of life.This solid and philosophers, and religious studies.The geography of this term is called the individual areas of the planet.By itself, the light - this is a social concept.Nevertheless, it has a specific scientific properties, traits and laws.
Nature and light sources
electromagnetic radiation generated in the process of interaction of charged particles.The best condition for this is the heat, which has a continuous spectrum.The maximum temperature depends on the radiation source.An excellent example of the process is the sun.Its radiation is close to that of the blackbody.Nature light on the sun is due to the heating temperature of 6000 K. In this case about 40% of the radiation is within sight.The maximum range of power is located near 550 nm.
light sources can also be:
- electronic shell of molecules and atoms during the transition from one level to another.Such processes allow to reach the linear range.Examples are LEDs and discharge lamps.
- Cherenkov radiation, which is formed by the motion of charged particles with the phase velocity of light.
- during braking photons.The result is a synchrotron or cyclotron radiation.
nature of light can be associated with luminescence.This also applies to artificial sources, and organic.Example: chemiluminescence, scintillation, phosphorescence, and others.
In turn, the light sources are divided into groups with respect to temperature characteristics: A, B, C, D65.The most difficult is observed in the spectrum of an absolutely black body.
Characteristics of light
subjectively perceives the human eye as the color of the electromagnetic radiation.Thus, light can give white, yellow, red, green tints.This is only a visual impression is associated with the frequency of radiation, whether it is for monochromatic or spectral composition.It is proved that photons can be distributed even in a vacuum.In the absence of the substance flow rate equal to 300,000 km / s.This discovery was made in the early 1970s.
at the boundary stream of light experiences a reflection or refraction.During the spread of it is scattered through the substance.It can be said that the optical parameters are characterized by the value of the refractive index, equal to the ratio of speeds in a vacuum and acquisitions.The isotropic distribution substances flow independent of direction.Here, the refractive index is represented by a scalar value, to determine the coordinates and time.In an anisotropic medium photons manifests itself in the form of the tensor.
In addition, the light is polarized and there.In the first case, the main quantity will determine the wave vector.If the stream is not polarized, it consists of a set of particles directed in random directions.
most important characteristic is the light and its intensity.It is determined by the photometric values such as power and energy.
basic properties of light
photons can not only interact, but also have a direction.As a result of contact with the outside environment flow undergoes reflection and refraction.These are the two fundamental properties of light.On reflection more or less clear: it depends on the density of matter and the angle of incidence.However, with the breaking of the situation is much more complicated.
For starters, you can consider a simple example: if you omit the straw into the water, then it will seem from the bent and shortened.This is the refraction that occurs at the boundary of the fluid and air.This process is determined by the direction of the ray distribution while passing through the border matter.When the flow of light touches the boundary between the media, its wavelength changes significantly.However, the frequency of the spread remains the same.If the beam is not orthogonal with respect to the border, and will undergo a change in wavelength and direction.
Artificial light refraction is often used for research purposes (microscopes, lenses, magnifiers).Also, to those sources are changing the characteristics of the wave points.
Classification light
Currently distinguish artificial and natural light.Each of these determined characteristic radiation source.
Natural light is a collection of charged particles from the chaotic and rapidly changing direction.This is caused by the electromagnetic field alternating voltage fluctuations.The natural sources include incandescent body, the sun, polarized gases.
Artificial light can be of the following types:
- local.It is used in the workplace, in the area kitchen, walls, etc.This lighting plays an important role in interior design.
- total.This uniform illumination of the entire area.Sources include chandeliers, floor lamps.
- combined.A mixture of the first and second types to achieve the perfect illumination of the room.
- emergency.It is extremely useful for blackouts.Power is produced mostly from batteries.
Sunlight
Today it is the main source of energy on Earth.It is no exaggeration to say that sunlight affects the all-important matter.This quantitative constant, which determines the energy.
In the upper layers of Earth's atmosphere contains about 50% infrared radiation and 10% of UV.Therefore, the quantitative component of the visible light is only 40%.
Solar energy is used in synthetic and natural processes.This photosynthesis and transformation of chemical forms, and heating, and much more.Thanks to the sun can enjoy the power of humanity.In turn, the light fluxes can be direct and scattered when they pass through the cloud.
Three major law
Since ancient times, scientists have been studying the geometric optics.Today, the fundamental laws of the world are as follows:
- law distribution.He says that in a homogeneous optical medium the light is distributed in a straight line.
- law of refraction.The light beam incident on the boundary of two media, and the projection of the intersection points lie on the same plane.This also applies to the place of the omitted touch perpendicular.The ratio of the sines of the angles of incidence and refraction is constant.
- law of reflection.Sink to the boundaries of the medium and the light beam projection lie on the same plane.The angles of incidence and reflection are equal.
perception of light
world around man of vision due to the ability of his eyes to interact with electromagnetic radiation.Light perceived retinal receptors, which can capture and respond to the spectral range of the charged particles.
In humans there are 2 types of sensitive eye cells: rods and cones.The first cause of the mechanism in the daytime with a high level of illumination.Sticks are also more sensitive to radiation.They allow a person to see at night.
Spotting colors are caused by light wavelength and direction.
