indicators (ratios) of refraction is called a kind of abstract number, which characterizes the refractive power of a transparent medium.Labeling it adopted the Latin letter n.There are an absolute refractive index and the coefficient of relative.
first calculated by one of two formulas:
n = sin α / sin β = const (where sin α - sine of the angle of incidence, and sin β - sine of the angle of refraction of the light beam entering in the medium from the void)
or
n = c / υλ (where c - speed of light in vacuum, υλ - speed of light in the medium under study).
There calculation shows how many times the speed of light changes its propagation in the time of transition from the vacuum in the transparent medium.Thus defined refractive index (absolute).To find the relative, using the formula:
n = n2 / n1.
That is, in this case considered the absolute refractive indices of the materials of different densities, such as air and glass.
Generally speaking, the absolute rates of any bodies, whether gaseous, liquid or solid, is always greater than 1. In general, the values range from 1 to 2. above 2, this value may be only in exceptional cases.The value of this parameter in some environments:
- refractive index glass (CZK) - 1.5163;
- air - 1.000292;
- glycerin - 1,473;
- ether - 1,358;
- ethyl alcohol - 1,363;
- carbon disulfide - 1,629;
- plexiglass - 1.49.
This value is applied to the very hardest natural substance on the planet, the diamond is 2.42.Very often, for scientific research and so on. D. Need to know the refractive index of water.This parameter is 1,334.
Since the wavelength - an indicator, of course, unstable, n is attributed to the letter index.Its value and helps to understand how to wave spectrum this ratio relates.When considering the same material, but with increasing wavelength of light, the refractive index will decrease.This circumstance is caused by expansion of the light spectrum when passing through the lens, prism and so on. D.
The magnitude of the refractive index can be determined, for example, as a substance dissolved in one another.This is useful, for example, in brewing, or when it is necessary to know the concentration of sugar, fruit or berry juice.This indicator is important in determining the quality of oil products, and jewelry when necessary to prove the authenticity of the stone, and so on. D.
To determine the refractive index using a special instrument called a refractometer.To use it, you first need to clean it with a soft cloth, and then apply 2-3 drops of the test substance on the prism included in the design.Then closes the special plate for daylight.
without the use of a substance range visible in the eyepiece of the device will be completely painted in blue.If you drop the prism ordinary distilled water, at the correct calibration of the instrument border of blue and white colors will be strictly zero point.In the study of other substances, it will move on a scale according to which the refractive index is peculiar to him.
