The main light quantities are luminous flux, illuminance and power light.
Surrounding objects emit radiant energy representing propagating in space electromagnetic oscillations. One of the main characteristics of electromagnetic hesitation is the wavelength, which can to be from fractions of a millimeter to several hundreds and even thousands of meters. The human eye perceives a relatively small the range of these waves. Radiation in the wavelength range, perceived human the eye in the form of colored spots of light are called the optical region of the spectrum of electromagnetic oscillations. Radiation length waves outside the visible region electromagnetic spectrum perceived by the human eye. Each wavelength corresponds to a specific color, resulting with the change of the wavelengths are changing and the colors perceives the human eye.
Luminous flux is the radiation power, which is measured at the light the sensation produced in the human eye. The unit of measurement of luminous flux F is the lumen (LM).
Illuminance is the luminous flux per unit surface. About the light intensity is judged by the density at which the luminous flux is distributed over the illuminated surface. The unit of illuminance is Lux (LX).
The illuminance E is the ratio between the luminous flux F, the fallen on the surface, to its area S:
E = F/S.
Surface illuminance is 1 Lux, if for each 1 m2 of its area fall luminous flux of 1 LM, i.e., 1 LX = 1 LM/1 m .
Intensity is a term that serves to characterize the distribution of light flow source, determines the density of the light flow in a given direction. Some light sources emit light the flow is uneven, i.e. with different intensity in different directions.
The unit of luminous intensity adopted Candela (CD), which is the main lighting unit, which is installed by special to the standard.
Author: E. A. Bannikov