Different Forms
Planck's law can be encountered in several forms depending on the conventions and preferences of different scientific fields. The various forms of the law for spectral radiance are summarized in the table below. Forms on the left are most often encountered in experimental fields, while those on the right are most often encountered in theoretical fields.
| with h | with ħ | ||
|---|---|---|---|
| variable | distribution | variable | distribution |
| Frequency |
Angular frequency |
||
| Wavelength |
Angular wavelength |
||
| Wavenumber |
Angular wavenumber |
||
These distributions represent the spectral radiance of blackbodies—the power emitted from the emitting surface, per unit projected area of emitting surface, per unit solid angle, per spectral unit (frequency, wavelength, wavenumber or their angular equivalents). Since the radiance is isotropic (i.e. independent of direction), the power emitted at an angle to the normal is proportional to the projected area, and therefore to the cosine of that angle as per Lambert's cosine law, and is unpolarized.
Read more about this topic: Planck's Law
Famous quotes containing the word forms:
“When we speak the word “life,” it must be understood we are not referring to life as we know it from its surface of fact, but to that fragile, fluctuating center which forms never reach.”
—Antonin Artaud (1896–1948)
“No rent-roll nor army-list can dignify skulking and dissimulation: and the first point of courtesy must always be truth, as really all the forms of good-breeding point that way.”
—Ralph Waldo Emerson (1803–1882)