Basic concepts and nouns


The following nouns and concepts are often used in infrared radiation theory.

1) Radiant energy

In infrared radiation theory, radiant energy refers to the total energy of an object emitting infrared radiation, symbol. The unit is Joule (J). The black body radiation is the sum of the total spectrum energy, the gray body is the total energy of the emissivity correction based on the black body radiant energy at the same temperature, and the sum of the effective infrared radiant energy of the selective emitter for the emissivity correction. For the laser, it is the radiant energy corresponding to a certain wavelength.

2) Radiation energy density

The radiant energy density is the infrared radiant energy emitted by an object in a unit volume, symbol, defined The unit is joules per cubic meter().

3) Radiant energy flux

Radiant energy flux is the infrared radiant energy emitted or received by an object in unit time, referred to as radiant flux, symbol, defined

The unit is (W).

4) Radiant flux density / emission / irradiance

Radiation flux density, radiance, and irradiance are the infrared radiant energy fluxes emitted or received by an object per unit area in watts per square meter ( ). It is customary to use the emission degree when describing the emission of an object, the symbol, defined

Irradiance, symbol, defined when describing the reception of an object

Radiative flux density is a general term that describes this concept by definition. In general, the radiation exit of an object is a function of temperature and wavelength.

5) Radiation intensity

Radiation intensity is the infrared radiation flux emitted by the infrared radiation source at a unit solid angle, symbol, defined

The unit is watts per sphericity ( ), which characterizes the ability of infrared radiation sources to emit infrared radiation.

6) Radiation brightness

The radiance is the infrared radiation flux emitted by the unitary angle of the infrared radiation source and the unit area when the angle between the normal and the surface of the infrared radiation source is θ, symbol, defined

The unit is watts per square meter ( ), which characterizes the extent to which infrared radiation sources emit infrared radiation. The radiance of an object is also a function of temperature and wavelength.

After all the above physical quantities are added with the lower angle, it becomes a physical quantity describing a certain wavelength of infrared radiation. For example, the radiant brightness is referred to as a single-color radiance or a spectral radiance. And so on.

When infrared radiation is incident on an object, absorption, reflection, and transmission will occur. In addition, the object also emits infrared radiation. These physical phenomena are described by the following concepts and nouns. In general, the absorptivity, reflectance, transmittance, emissivity, etc. of an object are a function of wavelength and temperature. The absorption rate, reflectance, transmittance, and emissivity may be different for not only different objects but also objects of different states (such as temperature, surface finish, etc.).

7) Absorption power / absorption rate

The absorptive power indicates the ability of an object to absorb infrared radiation incident thereon, and the absorption power is numerically expressed as the absorption rate. The absorption rate is dimensionless and is the ratio of the absorbed amount to the incident amount. Since the absorption rate is a function of wavelength and temperature, there is a spectral absorption rate and an average absorption rate

8) Reflective power / reflectivity

The reflection power indicates the ability of an object to reflect the infrared radiation incident thereon, and the reflection power is a reflection rate. The reflectivity is dimensionless and is the ratio of the amount of reflection to the amount of incident. Since the reflectance is a function of wavelength and temperature, there is a spectral reflectance and an average reflectance

9) Transmission power/transmittance

The transmission power indicates the ability of an object to transmit infrared radiation incident thereon, and the transmission power by a number is the transmittance. The transmittance is dimensionless and is the ratio of the amount of transmission to the amount of incident. Since the transmittance is a function of wavelength and temperature, there is a spectral transmittance and an average transmittance.

10) Launching power/emissivity

The emission power indicates the emission capability of the infrared radiation of the object, and the emission power by the number is the emissivity. The emissivity is dimensionless, the ratio of the amount of infrared radiation emitted by an object to the amount of infrared radiation emitted by the same temperature. Since the emissivity is a function of wavelength and temperature, there is a spectral emissivity and an average emissivity. For the black body, the spectral emissivity is equal to 1, so the average emissivity is also equal to.



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