What is the first radiation constant?
The first radiation constant is c_1 = 3.741771852e-16 W·m^2, exact by SI definition. It appears in Planck's blackbody law.
Open the interactive PhysRef tool →Key facts
| Value | 3.741771852e-16 W·m^2 |
|---|---|
| Symbol | c_1 |
| Relation | c_1 = 2π·h·c^2 |
| Exactness | Exact by SI definition (uncertainty 0) |
| Source | CODATA 2018 |
Frequently asked questions
What is the value of the first radiation constant?
c_1 = 3.741771852e-16 W·m^2, used in Planck's law for spectral radiant exitance.
How is c_1 defined?
c_1 = 2π·h·c^2, combining the Planck constant and the speed of light.
Is the first radiation constant exact?
Yes, because h and c are exact, so c_1 is exact.
Related pages
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