Radiation from an ideal absorber whose spectrum could only be explained by Planck's idea of quantized energy.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
A black body is an ideal absorber and emitter whose radiation spectrum depends only on its temperature. Classical physics predicted that the energy emitted at short wavelengths should grow without limit, the so-called ultraviolet catastrophe, which experiment showed to be wrong. In 1900 Max Planck resolved this by assuming that energy is exchanged in discrete quanta proportional to frequency. Hotter objects glow at shorter peak wavelengths, as described by Wien's displacement law, lambda_max x T = 2.898 x 10^-3 m K. The black body curve is one of the key tests of quantum theory.
Key ideas: A black body absorbs all radiation and emits a spectrum depending only on temperature. Wien's law: lambda_max x T = 2.898 x 10^-3 m K. Stefan-Boltzmann: power per area = sigma T^4, sigma = 5.67 x 10^-8 W per m2 K4. Hot objects shift from red to white to blue as T rises. The sun at 5800 K peaks near 500 nm.
Common mistakes and connections: Students think the object emits only at one wavelength; it emits a continuous distribution with a peak. Classical theory predicted an ultraviolet catastrophe (infinite energy at short wavelengths), which Planck solved with quantization. It marks the birth of quantum theory.
At 5800 K, like the Sun's surface, the black body curve peaks in the visible; Planck's law fixed the classical ultraviolet catastrophe. The interactive lesson shows this as a live animation or chart.
A heated iron bar glows dull red first, then orange, then white as its temperature rises.
Radiation from an ideal absorber whose spectrum could only be explained by Planck's idea of quantized energy.
Black Body Radiation is a intermediate topic in Atomic Structure & Periodicity. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Atomic Structure & Periodicity first: Electromagnetic Radiation, Wavelength and Frequency, Electromagnetic Spectrum.
The next topics in Atomic Structure & Periodicity are Planck's Quantum Theory and Photoelectric Effect.
Yes. The interactive lesson includes a self-check question on Black Body Radiation, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Black Body Radiation is topic 35 of 115 in Atomic Structure & Periodicity.