Light is a kind of light factor that illuminates all objects, but do you understand light? Today I provide some basic terms of light to let you know him better!
1. The nature of light:
The essence of light is electromagnetic wave, which is a very small part of the entire electromagnetic spectrum. Light is a form of energy;
Visible light is the part of the electromagnetic radiation spectrum that can cause human vision.
Visible light forms part of the so-called electromagnetic spectrum, which exists in radio and television signals, including infrared and ultraviolet radiation, x-rays, nuclear radiation and cosmic radiation. Among these electromagnetic radiations, only light waves are visible to the eyes of animals and humans. The spectrum also includes the standard 50 Hz alternating current (wavelength 6000 kilometers) and the visible part of the wavelength 380-780 nanometers (=10-9 meters). Different wavelengths give the human eye different color perceptions, ranging from red, orange, yellow, green, blue, indigo (that is, blue-violet) to purple.
2. Luminous flux (beam):
It is the light (number) emitted by the light source in lumens (lm). For example, if an energy-saving lamp emits 780 (lights), the total luminous flux (beam) is 780 lumens.
3. Brightness:
It is almost the same as the definition of illuminance. If we regard every object as a light source, then brightness is a description of the brightness of the light source, and illuminance just takes every object as the illuminated object. When the light beam hits the wooden board, we talk about the illuminance of the wooden board, and then the amount of light reflected by the wooden board to the human eye is called the brightness of the wooden board. Then there is the following formula: the brightness is equal to the illuminance multiplied by the reflectivity.
The illuminance of a white cloth and a black cloth at the same place in the same room is the same, but the brightness is different.
4. Illumination:
It is the light passing through each unit area, the unit is lx. (lm/m2)
5. Light intensity:
It is the number of rays passing through 1 solid angle, (the density of the passing beam). The unit of light intensity is the basic unit of photometry and one of the basic units of the International System of Units. In order to reproduce the unit of light intensity, the benchmark of light was originally a candle, so the unit of light intensity was long called (candle). Later, with the development of science and technology, the light reference was changed to a tungsten lamp and then to a black body. After 1948, the light intensity unit was officially named Candela (cd).
6. Glare, how to control glare:
There are extremely bright objects or strong brightness contrast in the field of view, which can cause discomfort or reduce vision, which is called glare. The glare that causes the reduced vision of the human eye is called disability glare; the glare that makes people feel unpleasant is called uncomfortable glare.
There are generally two ways to control glare: 1. Directly control the brightness of the light source or use light-transmitting materials to reduce the glare; 2. Use the protection angle of the lamp to control the glare.
7. Color temperature:
Since people describe the color table of the light source with the absolute temperature of the complete radiator that is equal to or similar to the chromaticity of the light source, the color table of the light source is also called the color temperature of the light source.
Color temperature: When the color of the light emitted by the light source is the same as that of the black body at a certain temperature, the temperature of the black body is called the color temperature of the light source.
8. Color temperature psychology
The color temperature below 3300k has a stable atmosphere and a warm feeling; the color temperature is 3000-5000K as the intermediate color temperature, which has a refreshing feeling; the color temperature above 5000k has a cold feeling. Under the illumination of high color temperature light source, if the brightness is not high, it will give people a kind of cloudy atmosphere; under the illumination of low color temperature light source, the brightness will be too high and people will have a stuffy feeling. When two light sources with large light color difference are used in the same space, the contrast will have a gradation effect. When the light color contrast is large, the brightness level can be obtained while the light color level is obtained.
9. Physiological basis of color vision:
The light emitted by the object passes through the cornea, aqueous humor, lens and vitreous body to focus the object image on the retina. The photoreceptor cells of the retina are transformed into nerve impulses, which are then transmitted to the high-level visual center of the brain to produce vision. There are two types of photoreceptor cells in the human retina: rod-shaped cells and cone-shaped cells. Rod-shaped cells have high sensitivity to light, and cone-shaped cells have low sensitivity to light. Therefore, only rod-shaped cells work under weak illumination. As the brightness continues to increase, the role of cone-shaped cells continues to increase, and finally cone-shaped cells play a leading role. Rod-shaped cells cannot distinguish colors, only cone-shaped cells have color perception.
