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:
“Your body must become familiar with its death—in all its possible forms and degrees—as a self-evident, imminent, and emotionally neutral step on the way towards the goal you have found worthy of your life.”
—Dag Hammarskjöld (1905–1961)
“A monarchy is the most expensive of all forms of government, the regal state requiring a costly parade, and he who depends on his own power to rule, must strengthen that power by bribing the active and enterprising whom he cannot intimidate.”
—James Fenimore Cooper (1789–1851)