Wien Displacement Law Calculator

Wien displacement law gives the wavelength at which a blackbody radiates most intensely. The peak shifts to shorter (bluer) wavelengths as temperature increases. The Sun peaks in green at 501 nm.

🌈 Thermal Radiation📐 λ = b/T🌟 Blackbody
Temperature T (K)
Or Peak Wavelength (nm)

Enter temperature OR wavelength

Please enter valid values.

Formula & Reference

VariableSymbolFormulaUnits
Peak Wavelengthλmaxλmax = b/Tm
TemperatureTT = b/λmaxK
Wien Constantb2.898 × 10⁻³ m·Km·K

Step-by-Step Examples

Example 1
Sun

T = 5778 K.

  • lambda_max = 2.898e-3/5778 = 501 nm
✓ 501 nm — green (near peak of eye sensitivity)
Example 2
Human Body

T = 310 K (37 deg C).

  • lambda_max = 2.898e-3/310 = 9.35 um
✓ 9.35 um — mid-infrared (thermal camera range)
Example 3
Find Star Temperature

Star peaks at 100 nm.

  • T = b/lambda = 2.898e-3/100e-9 = 28,980 K
✓ ~29,000 K — O-class hot blue star

Real-World Applications

🌟
Stellar Classification
OBAFGKM sequence is temperature order; Wien law links peak wavelength to stellar type.
📷
Thermal Cameras
Cameras tuned 8-14 um detect human body radiation (peak ~9.5 um at 37 deg C).
🛰️
Remote Sensing
Satellites measure surface temperature from IR peak wavelength via Wien law.
💡
Incandescent Bulbs
Tungsten at 2700 K peaks at 1074 nm — most energy is infrared, only ~10% visible.

Common Mistakes to Avoid

⚠️
T must be in Kelvin

Wien constant b = 2.898e-3 m*K. Room temperature 20 deg C = 293 K, not 20 K.

⚠️
Convert nm to m

If using wavelength in nm: lambda(m) = lambda(nm) * 1e-9 before applying T = b/lambda.

⚠️
Peak is not the only emission

Objects emit across all wavelengths. lambda_max is where emission is greatest, not exclusive.

Frequently Asked Questions

Why does the Sun appear white/yellow if it peaks in green? ▾
The Sun emits across the full visible spectrum nearly uniformly. Our eyes and brain perceive this as white. Atmospheric scattering selectively removes some blue, making it appear yellow-white.
What temperature corresponds to peak visible light? ▾
Visible range 400-700 nm: T = 4140-7245 K. Stars in this range appear white to blue-white.
How are star temperatures measured? ▾
Spectrophotometry measures peak wavelength of starlight. Wien law converts to surface temperature without knowing the star distance.
What is the CMB temperature and peak wavelength? ▾
CMB at T = 2.725 K peaks at lambda = 2.898e-3/2.725 = 1.063 mm — microwave range. Photons were visible light just after Big Bang when T was ~3000 K.
Does Wien law apply to non-blackbodies? ▾
Wien law gives peak for ideal blackbody (emissivity = 1). Real objects may have different spectral peaks due to wavelength-dependent emissivity.

Related Physics Calculators

🔥 Stefan-Boltzmann💡 Photon Energy🌟 Stellar Luminosity🌈 Wavelength Energy🌀 Doppler Redshift

Formula Explorer connections

Interpretation: This formula tracks heat, temperature, work, entropy or transport in a thermodynamic system. Assumption: Use absolute temperature where required and consistent energy units. Constant properties, equilibrium, ideal gases or negligible losses may be assumed.

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