Wien’s Displacement Law
Wien’s Displacement Law
A hot body radiates most strongly at a wavelength that shortens as it gets hotter — why heated metal glows red then white.
Wien’s law gives λ_max = b/T. where b is Wien’s constant and T the absolute temperature.
Inputs
b := 2.898e-3 m·K=2.9e-03 K·m
T := 1000 K=1000 K
Divide Wien’s constant by temperature.
lambda_max := b/T=2.9e-03 mm
Results
At 1000 K the peak is in the infrared; the Sun’s ~5800 K peaks in visible light. This law underlies pyrometry and thermal imaging.
Assumptions & limitations
- Ideal black-body emitter.
- Absolute (kelvin) temperature.
- Thermal equilibrium.