How did Max Planck’s study of blackbody radiation help lead to quantum theory?

In the late 19th century, classical physics failed to explain the spectrum of blackbody radiation. Calculations based on classical electromagnetic theory predicted that spectral intensity would increase infinitely with frequency, a discrepancy known as the ultraviolet catastrophe.12

In 1900, Max Planck resolved this by proposing that the oscillators at the surface of a blackbody emit and absorb electromagnetic radiation only in discrete packets, or quanta. He determined that the energy of each packet is directly proportional to its frequency, expressed by the equation $E=hf$, where $h$ is now known as Planck’s constant.134

By assuming energy was quantized rather than continuous, Planck derived a formula that matched experimental observations across all wavelengths. This departure from classical mechanics established the foundation for quantum theory, as it demonstrated that the microphysical world could not be described by classical laws. Planck’s work eventually led to further breakthroughs, including Albert Einstein’s concept of light quanta and the development of wave-particle duality.352