Planck made important contributions to theoretical physics and especially to quantum theory. The article "Über das Gesetz der Energieverteilung im Normalspektrum" ("On the Law of Energy Distribution in the Normal Spectrum") by Max Planck, published in 1901, marks the birth of quantum theory. In this groundbreaking work, Planck introduces the concept of quantized energy and formulates the Planck radiation law. **Key Points:** 1. **Blackbody Radiation Problem:** Planck addresses the long-standing issue of blackbody radiation, attempting to explain the spectral distribution of electromagnetic radiation emitted by a perfect absorber and emitter of radiation. 2. **Quantization of Energy:** Planck proposes a revolutionary idea that energy is quantized, not continuous. He introduces the concept of energy quanta or "quanta of action" (later termed "quantum") to describe the discrete packets of energy associated with oscillators in a blackbody. 3. **Planck's Radiation Law:** Formulating his radiation law, Planck successfully derives a mathematical expression that accurately describes the spectral distribution of blackbody radiation. This law introduces the famous Planck constant (h). 4. **Advent of Quantum Theory:** The quantization of energy marks a departure from classical physics and lays the foundation for quantum theory. Planck's work becomes a cornerstone for the later development of quantum mechanics. 5. **Recognition and Impact:** Planck's groundbreaking ideas are initially met with skepticism but later gain widespread acceptance. His work revolutionizes the understanding of atomic and subatomic processes and earns him the Nobel Prize in Physics in 1918. 6. **Historical Significance:** Planck's article is a pivotal moment in the history of physics, initiating a paradigm shift and influencing subsequent generations of physicists, including Albert Einstein and Niels Bohr, who further develop quantum theory. A fundamental parameter in Physics, the so called Planck's constant, which gives the relationship between the energy of a photon and its frequency, is named after Planck. see also / download at: Wiley Online Library

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