1. Stefan-Boltzmann Law: This is perhaps the most common understanding of the "law of radiation." It states that the total energy radiated per unit surface area of a black body is proportional to the fourth power of its absolute temperature. Mathematically:
```
P = σ * A * T^4
```
Where:
* P is the total power radiated
* σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W m^-2 K^-4)
* A is the surface area of the object
* T is the absolute temperature in Kelvin
2. Planck's Law: This law describes the spectral distribution of electromagnetic radiation emitted by a blackbody at a given temperature. It states that the energy density of radiation at a particular frequency is proportional to the frequency cubed and inversely proportional to the exponential of the frequency times Planck's constant divided by Boltzmann's constant times the temperature.
3. Wien's Displacement Law: This law relates the peak wavelength of the radiation emitted by a blackbody to its temperature. It states that the wavelength at which the radiation intensity is maximum is inversely proportional to the temperature:
```
λ_max = b/T
```
Where:
* λ_max is the wavelength at which the spectral radiance is maximum
* b is Wien's displacement constant (2.8977729 x 10^-3 m⋅K)
* T is the absolute temperature in Kelvin
4. Kirchhoff's Law of Thermal Radiation: This law states that the emissivity of a body at a given temperature is equal to its absorptivity at that temperature. This means that a good absorber of radiation is also a good emitter of radiation.
5. Lambert's Cosine Law: This law describes the intensity of radiation emitted from a surface as a function of the angle between the direction of emission and the surface normal. It states that the intensity is proportional to the cosine of this angle.
In summary:
The "law of radiation" can refer to different aspects of how electromagnetic radiation interacts with matter. The most common interpretation is the Stefan-Boltzmann Law, which describes the total energy radiated by a blackbody. However, other important laws like Planck's Law, Wien's Displacement Law, Kirchhoff's Law, and Lambert's Cosine Law also contribute to our understanding of radiation phenomena.
