1. What is the meaning of luminous intensity (luminosity)?
Answer: Luminous intensity (luminosity, I) is defined as: the luminous intensity of a point source in a certain direction, that is, the amount of light emitted by the illuminant per unit time, also referred to as luminosity, commonly used in candlelight (cd, candela), An international candlelight is defined as a luminosity of 120 grams of grain burned per hour from a candle made of whale fat, equal to 0.0648 grams.
2. What is the unit of luminous intensity (luminance)?
A: The common unit of luminous intensity is candlelight (cd, candela), and the international standard candlelight (lcd) is defined as the ideal blackbody at the platinum freezing point temperature (1769 ° C), perpendicular to the black body (its surface area is 1 m2) in the direction of 600,000 points One of the luminosity, the so-called ideal black body means that the emissivity of the object is equal to 1, the energy absorbed by the object can be completely radiated, so that the temperature is kept evenly fixed, and the international standard candle (candela) is interchanged with the old standard candle (candle). The relationship is 1candela=0.981candle
3. What is luminous flux? What is the unit of luminous flux?
A: The luminous flux (φ) is defined as the energy emitted by a point source or a non-point source in a unit of time. The radiant flux that can be perceived by a person (the radiant flux that a person can perceive) is called luminous flux. The unit of luminous flux is lumens (abbreviation lm), and lumens (lumen or lm) are defined as the luminous flux of a light source of an international standard candle passing through a unit solid arc angle. Since the entire spherical area is 4πR2, the first-class bright luminous flux is equal to one candle. The 1/4 π of the emitted light flux, or the spherical surface has 4π, so according to the definition of lumens, a point source of cd will radiate 4π lumens, that is, φ (lumen) = 4πI (candle), assuming that ΔΩ is a small solid arc Angle, in the △ Ω solid angle luminous flux △ φ, then △ φ = △ Ω I
4. What is the meaning of one foot candlelight?
A: One foot of candlelight refers to the illuminance on a face that is one foot away from a light source (point or non-point source) and orthogonal to the light, abbreviated as 1ftc (1lm/ft2, lumens/ft2), ie The luminous flux received within a square foot is 1 lumen, and 1ftc = 10.76lux
5. What is the meaning of one meter candle?
A: One meter of candle light refers to the illuminance on a surface that is one meter away from a light source (point source or non-point source) and orthogonal to the light. It is called lux (also written as lx), that is, per square meter. The luminous flux received within the lumen is 1 lumens (lumen/m2)
What is the meaning of 6.1lux?
A: The luminous flux received per square meter is 1 lumens of illumination.
7. What is the meaning of illuminance?
A: Illuminance (E) is defined as the luminous flux received by the illuminated area of ​​the object, or the luminosity of the object illuminated by light per unit area per unit of time, in meters of candlelight or foot-candle ( Ftc)
8. What is the relationship between illuminance and luminosity and distance?
A: The relationship between illuminance and luminosity and distance is: E (illuminance) = I (luminosity) / r2 (distance square)
9. What are the factors related to the illumination of the subject?
A: The illumination of the subject is related to the luminous intensity of the light source and the distance between the subject and the light source, regardless of the color, surface properties and surface area of ​​the subject.
(Assistant editor: xiaohu)
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