Planck Bλ
Blackbody spectral radiance per unit wavelength (SI).
Inputs
Results
B_λ (W·sr⁻¹·m⁻³)
26,375,669,866,614.81
How to Use This Calculator
- Enter the blackbody temperature T (K) -- Sun surface ~5778 K, room temperature ~293 K.
- Enter the wavelength lambda (m) -- visible light: 380-700 nm = 3.8e-7 to 7e-7 m.
- Review spectral radiance in W per sr per m3.
- Sweep wavelength across the visible spectrum to see how radiance peaks shift with temperature (Wien's law).
- Compare spectral radiance at different temperatures to understand why hotter objects appear bluer.
How the result changes with T (K)
| T (K) | B_λ (W·sr⁻¹·m⁻³) |
|---|---|
| 10,000,001 | 1,322,601,481,143,404,300 |
| 35,000,001 | 4,633,866,087,087,884,000 |
| 65,000,000 | 8,607,384,144,631,023,000 |
| 90,000,000 | 11,918,649,364,334,584,000 |
What each input means
- T (K)
- Sun ~5778 K.
- λ (m)
- 500 nm green.
How this is calculated
Formula
B_λ = 2hc² / (λ⁵ × (e^(hc/λkT) − 1))Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
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