NSW · HSCModule 7
Blackbody (Wien and Stefan-Boltzmann) calculator
Three modes: peak wavelength from temperature, temperature from peak wavelength, and radiated power from temperature and area.
Inputs
Result
Peak wavelength λ_max
5.016e-7m
≈
501.6nm
Wien's law: λ_max T = b, where b ≈ 2.898 × 10⁻³ m·K.
How this calculator works
Wien's law λ_max = b/T tells you the colour of a hot object. Stefan-Boltzmann P = σAT⁴ tells you how much total power it radiates. The Sun, fire, light bulbs, and stars are all approximate blackbodies.
Common questions
- What is Wien's displacement law?
- λ_max × T = b, where b ≈ 2.898 × 10⁻³ m·K. The peak wavelength of a blackbody's emission shifts shorter as the object gets hotter.
- What is the Stefan-Boltzmann law?
- The total power radiated per unit area by a blackbody is σT⁴, where σ ≈ 5.670 × 10⁻⁸ W/(m²·K⁴). For a surface of area A, total power is P = σAT⁴.
- Why does the Sun peak in green?
- The Sun's surface temperature is about 5778 K, giving λ_max ≈ 502 nm (green-blue). Our eyes evolved sensitivity peaked near this wavelength, which is why grass looks bright and the Sun looks white when viewed against the sky.
- What is emissivity?
- A factor 0 ≤ ε ≤ 1 multiplying P for real (non-ideal) surfaces. A perfect blackbody has ε = 1. This calculator assumes ε = 1; multiply your result by ε for real surfaces.