LearnLight & spectraSome maths
Wien's displacement law
The wavelength at which a blackbody radiates most strongly is inversely proportional to its temperature.
Why it matters
It converts colour into temperature. Measure where a star's spectrum peaks and you know how hot its surface is without ever going there.
The maths, in layers
1 · Intuition
Hotter bodies peak at shorter, bluer wavelengths.
2 · The equation
λ_max = b / T, b = 2.898 × 10⁻³ m·K
- λ_max
- peak wavelength, metres
- T
- temperature, kelvin
3 · Where it comes from
The Sun at 5,772 K peaks at 502 nm — green, in the middle of the visible band our eyes evolved to use. That is not a coincidence.