- Mathematical definition
- Relation to other radiometric quantities
- SI radiometry units
- References
In radiometry, radiant energy density is the radiant energy per unit volume.[1] The SI unit of radiant energy density is the joule per cubic metre (J/m3).
Mathematical definition
Radiant energy density, denoted we ("e" for "energetic", to avoid confusion with photometric quantities), is defined as[2]
where
- ∂ is the partial derivative symbol;
- Qe is the radiant energy;
- V is the volume.
Relation to other radiometric quantities
Because radiation always transmits the energy,[2] it is useful to wonder what the speed of the transmission is. If all the radiation at given location propagates in the same direction, then the radiant flux through a unit area perpendicular to the propagation direction is given by the irradiance:[2]
where c is the radiation propagation speed.
Contrarily if the radiation intensity is equal in all directions, like in a cavity in a thermodynamic equilibrium, then the energy transmition is best described by radiance:[3]
Radiant exitance through a small opening from such a cavity is:[4]
These relations can be used for example in the black-body radiation equation's derivation.
SI radiometry units
{{SI radiometry units}}References
2. ^1 2 Karel Rusňák. Přenos energie elektromagnetickým vlněním. Department of Physics, Faculty of Applied Sciences, University of West Bohemia. 2005-11. Visited 2013-10-06
3. ^Max Planck. The Theory of Heat Radiation. Equation 21. 1914.
4. ^Max Planck. The Theory of Heat Radiation. Equation 7. 1914.
- Bike SF 2010
- BikeShare
- Bike shed
- Bikeshed
- Bikeshed color
- Bikeshed coloring
- Bike shed discussion
- Bikeshed discussion
- Bikesheddy
- Bikeshed effect
- Bikeshed problem
- Bike shop
- Bike shorts
- Bike Shorts
- Bikes Not Bombs
- Bikes-On-Board
- Bike (song)
- Biketawa Declaration
- Bike the Drive
- Bike tires
- Bike touring
- Bike Tour of Philadelphia
- Bike-to-Work Day
- Bike trail
- Bike trailer