The unit of light intensity is a major SI units. By international agreement on January plug in car

For such power sources of light measured in different directions and build a vector diagram (indicatrix). The curve drawn through the end of vectors corresponding to a certain scale in force in some light on-direction, gives an idea of the intensity distribution source. To introduce the concept of non-isotropic source of secondary spherical power light / ", which is defined by where F - the full flow of light source.
If the light source has significant size, then we can talk about the power of light elements on its surface. Then, under the formula (3.6) should be understood luminous flux that is emitted element surface within the angle o'Q, full intensity in a certain direction is the sum or the integral over the entire surface.
Full luminous flux describes the light source and its value can not be changed in any optical device. Action plug in car heater optical instruments limited to the redistribution of flux. Such, for example, the effect plug in car heater of signaling devices, projectors, which in some areas can be increased intensity a million times.
The unit of light intensity is a major SI units. By international agreement on January plug in car heater 1, 1948 introduced a new standard of light that plays with the highest possible precision light unit quantities: intensity, luminous flux, illumination plug in car heater and brightness. The primary standard of light (Fig. 3) is a light source that meets international requirements and production emits as a black body. In the USSR this standard in 1948 created in photometric laboratories Scientific Research Institute of Metrology PM Tyhodyeyev. plug in car heater Scheme of the structure of the USSR State standard light shown in Fig. 3. The tube 2 of processed thorium oxide (T1I02) placed in the crucible 1 of the same material. In the crucible contained about 190 grams of chemically pure platinum 3. The space between the quartz crucible and the outer vessel 4 filled with thorium oxide 5. bowl / heated to cure (melting) platinum (2042.5 K), and molten platinum maintains a constant temperature radiator 2. Tube and crucible made of thorium oxide, because it is quite refractory and does not pollute platinum. Clean platinum checked temperature coefficient = 1.3901 resistance. Luminous flux, which radiates inner cavity of the tube 2, comes through the window 6 in total internal reflection prism 7, and 8 through the lens diaphragm 9 reaches the plate 10 is used as a reference for comparison with the quartz lamp 11. The entire plug in car heater vessel is heated in a high-frequency induction oven.
Candela is the strength of light at which the brightness of the full radiator at hardening platinum is 60 cd 1 cm3. From this definition, it follows that Veo is candela of intensity that is emitted in the direction perpendicular to the surface plug in car heater of 1 cm2 blackbody temperature curing platinum. This definition of intensity existed plug in car heater before 1979, when the XVI General Conference on Weights and scales plug in car heater adopted a new definition; Candela is the strength of light in a given direction of a source that emits monochromatic light frequency 540 Hz 10i2, whose energy intensity in that direction is V6S3 W / Wed, _: It allows you to play Candela without creating black tilaTscho accordingly makes it possible to increase the accuracy of its determination by radiometry technology, that measure power (energy) radiation, which approached error error photometric best comparisons. But so far there is no information plug in car heater on experimental work performed on the basis of a new definition of Candela. "'With the unit of luminous intensity based on the formula (3.7) can be defined unit of luminous flux lumen.
E. Illumination Light stream and can come from non-self-luminous bodies that reflect or scatter the light that falls on them. Therefore, a number plug in car heater of practical plug in car heater and scientific tasks necessary plug in car heater to know how many luminous flux incident on a particular plug in car heater body part. For this physical quantity injected light. Illumination is numerically equal to the full luminous flux incident plug in car heater on a surface element, to the area of
Where a - angle between the normal to the plane of dS, which determine light, plug in car heater i the direction of light, d S n - a plane perpendicular to the flow, I - intensity point source. Energy illumination unit in SI is watts per square plug in car heater meter (W / m'2).
Brightness V. For many lighting tasks can be considered plug in car heater some sources point. However, the size of most sources can not be neglected. To characterize plug in car heater these self-luminous and nesamosvitnyh (glow reflected light) sources put the value of photometric brightness in a certain direction. It characterizes the radiation luminous surface in that direction. Brightness is determined plug in car heater flux, which refers to a certain direction unit apparent surface in the unit solid angle.
SvitnistR. If there is a finite source of light (or a glowing, luminous reflected light), the luminance source called surface density