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How It Works
Wien's Displacement Law (λmax = b/T) relates the peak emission wavelength of a blackbody to its temperature. Hotter objects peak at shorter (bluer) wavelengths; cooler objects peak at longer (redder) wavelengths. The constant b = 2.8978 × 10−3 m·K.
Example Problem
The Sun's surface temperature is about 5,778 K. At what wavelength does it emit most strongly?
- λmax = 2.8978 × 10−3 / 5,778
- λmax ≈ 501 nm (green-yellow visible light)
Frequently Asked Questions
What is a blackbody?
A blackbody is an idealized object that absorbs all incoming radiation and re-emits it in a characteristic spectrum that depends only on its temperature. Stars, molten metal, and the cosmic microwave background approximate blackbodies.
Why do hot objects glow red then white?
As temperature rises, the peak wavelength shifts from infrared into visible red, then through orange, yellow, and eventually white (a mix of all visible wavelengths). Wien's Law quantifies this shift.
How is Wien's Law used in astronomy?
Astronomers measure the peak wavelength of a star's spectrum and use Wien's Law to determine its surface temperature. For example, a star peaking at 290 nm (ultraviolet) has T ≈ 10,000 K.
Related Calculators
- Doppler Effect Calculator — analyze frequency shifts of waves.
- Einstein Equation Calculator — mass-energy equivalence in radiation.
- Radioactive Decay Calculator — nuclear radiation processes.
- Temperature Conversion Calculator — convert temperatures used in Wien's displacement law.
- Frequency Converter — convert radiation frequency units between Hz, THz, and GHz.
Reference: Lindeburg, Michael R. 1992. Engineer In Training Reference Manual. Professional Publication, Inc. 8th Edition.