The Sun's surface is ~5778K. What is its peak emission wavelength?

Λ_max = 2.898×10⁻³ / 5778.

At what temperature does an object peak in the visible range (~550nm)?

You can work it out this way: solve Wien's Law for T: T = b/λ_max.

How much more power does a 6000K star emit compared to a 3000K star?

P ∝ T⁴; ratio = (6000/3000)⁴ = 16.

Pro 🔒~20 min

Blackbody Spectrum

Explore thermal radiation and the quantum revolution

How it works

A blackbody is an ideal object that absorbs all incident radiation and emits radiation based solely on its temperature. As temperature increases, the peak emission wavelength shifts to shorter wavelengths (Wien's Law) and total power increases dramatically (Stefan-Boltzmann). Classical physics predicted infinite emission at short wavelengths (ultraviolet catastrophe). Planck resolved this by quantizing energy, birthing quantum mechanics.

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Step-by-step

Use the temperature slider to change the object's temperature.
Observe the emission spectrum shift from infrared (red glow) to visible white.
The spectrum peak follows Wien's Law.
Compare with the failed classical Rayleigh-Jeans prediction.

Key formulas

$\lambda_{max} = \frac{b}{T}$ Wien's Displacement Law (b = 2.898×10⁻³ m·K)
$P = \sigma A T^4$ Stefan-Boltzmann Law
$E = h\nu = \frac{hc}{\lambda}$ Photon energy (Planck)

Frequently asked questions

The Sun's surface is ~5778K. What is its peak emission wavelength?: Λ_max = 2.898×10⁻³ / 5778.
At what temperature does an object peak in the visible range (~550nm)?: You can work it out this way: solve Wien's Law for T: T = b/λ_max.
How much more power does a 6000K star emit compared to a 3000K star?: P ∝ T⁴; ratio = (6000/3000)⁴ = 16.