Radiative transfer

Radiative transfer (also called radiation transport) is when energy transfers through electromagnetic radiation. Radiation is made through absorption, emission, and scattering. The equation of radiative transfer (also called the radiative transfer equation, or RTE) describes these interactions using math. Equations of radiative transfer are used in many fields of science. These fields can be optics, astrophysics, atmospheric science, and remote sensing. Some of the analytic solutions for the equation exist. These equations are usually only in simpler forms. In more complicated equations, like equations with scattering effects, different methods are required. This article is mostly focused on radiative equilibrium.

 Definitions 
A radiation field is an area of space where electromagnetic radiation exists. Scientists describe this radiation using spectral radiance (sometimes called specific intensity).
Spectral radiance measures the amount of energy that runs through a small amount of area in a certain direction. Radiation can travel in any direction. The energy can move both forward and backward for every direction. The energy in this small piece of area is measured by the time interval, the amount of area the radiation hits,the angle that this radiation hits, and the frequency of the radiation. This can be written using this differential equation: is the spectral radiance (the subscript means that the spectral radiance is a function of , or radiation frequency)

 is the area
 is the position
 is the time
 is the solid angle
 is the direction
 is the angle between the radiation and the area (the unit vector  makes a perpendicular angle with the area)
 to are the radiation frequencies that the spectral lines are measured at.

The units of spectral radiance are energy/time/area/solid angle/frequency. In MKS units, this is  (watts per square-metre-steradian-hertz).

 Related pages 
 Beer-Lambert law
 Optical depth
 Planck's law

 References 

 Further reading 










Category:Electromagnetic radiation