# Reflection of light.

Some laws of physics is hard to imagine without the use of visual aids.This does not apply to all of the usual light falling on different objects.Thus at the interface separating two media, there is a change in direction of the light rays if this boundary is much larger than the wavelength.When this reflected light is caused when part of its energy back into the first medium.If a portion of the rays penetrate to a different environment, it is their index.In physics flow of light energy incident on the boundary between two different media, called the incident, and one that returns from her first environment - reflected.It is the relative position of these rays determines the laws of reflection and refraction of light.

## terms

angle between the incident beam and a line perpendicular to the interface of two media, reduced to the point of incidence of light energy flux, called the angle of incidence.There is another important indicator.This reflection angle.It occurs between the reflected beam and the perpendicular line, reduced to the point of his fall.The light can propagate in a straight line only in a homogeneous medium.Different environment differently absorb and reflect radiation of light.The reflection coefficient is a quantity that characterizes the reflectivity of the material.It shows how many brought light on the surface of the medium energy will be the one that will take her from the reflected radiation.This ratio depends on a number of factors, one of the most important is the angle of incidence of light and composition.Total reflection of light occurs when it strikes the object or substance with a reflective surface.For example, it might be in contact with the rays on a thin film of liquid mercury and silver deposited on the glass.Total reflection of light in practice quite often.

## Laws

laws of reflection and refraction of light were formulated by Euclid still in the III century.BC.e.All of them have been established experimentally and is easily confirmed by purely geometrical Huygens' principle.According to him, any point of the medium, which comes to outrage, is a source of secondary waves.

first law of reflection of light: the incident and reflected beam and a line perpendicular to the interface, restoring to the point of incidence of the light beam in the same plane.On the reflecting surface plane wave, the wave surface which are strips.

Another law states that the angle of reflection equals the angle of incidence of light.This is because they have mutually perpendicular directions.Based on the principles of equality of triangles, it follows that the angle of incidence equals the angle of reflection.It's easy to prove that they lie in the same plane perpendicular to the line, reduced to the interface at the point of incidence.These important laws hold for the reverse light.Because of the reversibility of the energy beam propagating along the path of reflection, will be reflected on the way the incident.

## Properties reflecting bodies

vast majority of objects only reflect the incident light beam to them.However, they are not the source of light.Well-lit body perfectly visible from all sides, since the radiation is reflected from the surface and scattered in different directions.This phenomenon is called diffuse (scattered) reflection.It occurs when the light on any surface roughness.To determine the path of the beam reflected from the body at the point of his fall held a plane tangent to the surface.Then, in relation to her build angles of incidence and reflection.

## Diffuse reflection

only because of the existence of scattered (diffuse) reflection of light energy, we distinguish between items that are not capable of emitting light.Any body will be completely invisible to us, if the dispersion of rays will be zero.

Diffuse reflection of light energy does not cause human discomfort in the eyes.This stems from the fact that not all of the light returns to the initial medium.Because of the snow reflects about 85% of the radiation from the white paper - 75%, well on the black suede - only 0.5%.When reflected light from the various beams are directed rough surfaces randomly with respect to each other.Depending on the extent to which the surface reflects light rays, they are called matt or specular.Still, these concepts are relative.The same surface can be mirrored and opaque at different wavelengths of incident light.Surface that evenly disperses the beams in different directions, it is considered absolutely opaque.Although the nature of these objects there is little, it is very close to the unglazed porcelain, snow, drawing paper.

## Mirror Mirror

rays of light is different from other kinds that when falling energy beam onto a smooth surface at a certain angle are reflected in the same direction.This phenomenon is familiar to all who once enjoyed mirror the rays of light.In this case it is a reflecting surface.This category includes other body.By the mirror (reflecting) surfaces include all optically smooth objects if inhomogeneities and dimensions of irregularities on them are less than 1 micrometer (do not exceed the wavelength of light).For all such surfaces apply the laws of light reflection.

## reflection of light from different mirror surfaces

The technique is often used a mirror with a curved reflecting surface (spherical mirror).Such objects are bodies having a shape of a spherical segment.In the case of parallel rays of light reflected from such surfaces strongly disturbed.However, there are two types of mirrors:

• concave - reflect the light from the inner surface of the spherical segment, they are called to gather, because the parallel light beams after reflection from them going at one point;

• Convex - reflect light from the outer surface, the parallel rays are scattered by the side, which is why convex mirrors called scattering.

## Options reflection of light rays

beam incident nearly parallel to the surface, only slightly touches it, and then is reflected at a much obtuse angle.Then he continues on his way at a very low trajectory, most situated to the surface.Ray falling almost vertically reflected at an acute angle.The direction of the reflected beam is already close to the path of the incident beam that is fully consistent with the laws of physics.

Refraction of light reflection is closely related to other phenomena of geometrical optics, such as refraction and total internal reflection.Often, the light passes through the boundary between two media.Refraction of light is called a change in direction of the optical radiation.It occurs when it passes from one medium to another.Refraction of light has two patterns:

• beam passed through the boundary between the media, is situated in a plane which passes through the perpendicular to the surface and the incident beam;

• angle of incidence and refraction are related.

Refraction always accompanied by the reflection of light.The amount of energy reflected and refracted beams rays equal to the energy of the incident beam.Their relative intensity depends on the polarization of the light in the incident beam and the incident angle.On the laws of refraction of light based device many optical devices.

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