Case 1
- Temperature
- 5772K
502.039493nm
Open with these valuesWien's Displacement Law Calculator
502.039493nm
Result: 502.039493 nmDivide the Wien constant by the absolute temperature and you get the wavelength at which a blackbody shines brightest. Hotter means shorter: the Sun peaks near 502 nm in green light, a filament near 966 nm in the infrared. Temperature must be in kelvin, so add 273.15 to Celsius first.
Worked examples
Case 2
- Temperature
- 300K
9,659.239850nm
Open with these valuesCase 3
- Temperature
- 2.725K
1,063,402.552294nm
Open with these valuesHow it's calculated
λ_max = b ÷ T
- StepEnter the absolute temperature of the surface in kelvin.
- StepA Celsius reading? Add 273.15 before entering it.
- StepRead the wavelength of the emission peak in nanometres.
- ResultDivide by a billion if you need the answer in metres.
Reference table
| Temperature (K) | What that is | Peak wavelength (nm) |
|---|---|---|
| 2.725 | cosmic microwave background | 1063402.552294 |
| 300 | room temperature, far infrared | 9659.239850 |
| 1000 | dull red heat | 2897.771955 |
| 3000 | incandescent filament | 965.923985 |
| 5772 | the Sun's surface, green light | 502.039493 |
| 6000 | a slightly hotter star | 482.961993 |
Questions
How do I calculate the peak wavelength with Wien's law?
Divide the Wien displacement constant by the absolute temperature: λ_max = b / T, with b = 2.897771955 × 10⁻³ m·K and T in kelvin. For the Sun's surface at 5772 K that gives about 502 nm, in green light.
What is Wien's displacement law?
It describes how the wavelength at which a blackbody radiates most strongly shifts with temperature. The peak wavelength is inversely proportional to the absolute temperature, so the hotter the object, the shorter the peak. It is why heated metal glows red, then orange, then white.
What is the Wien displacement constant?
It is b = 2.897771955 × 10⁻³ metre-kelvin. Like the Stefan-Boltzmann constant it has been an exact value since the SI revision of 2019, because it follows from the defined Planck, Boltzmann and light-speed constants rather than from a measurement.
Why must the temperature be in kelvin?
The law uses absolute temperature, measured from absolute zero, so the value has to be in kelvin and strictly positive. Convert by adding 273.15 to a Celsius reading, turning 25 °C into 298.15 K. At or below 0 K the law is undefined.
How does this relate to the Stefan-Boltzmann law?
Both describe blackbody radiation but answer different questions. Wien's law tells you where the emission peaks, which is the colour; the Stefan-Boltzmann law tells you how much total power comes out. Together they fix the shape and the brightness of the spectrum.
Sources and last check
Information, not professional advice.