Planck's theory, specifically Planck's quantum theory, is not based on an electromagnetic (EM) standing wave that does not expand. Instead, it is a foundational theory in quantum physics that revolutionized our understanding of the behavior of energy at the smallest scales.
Max Planck proposed his quantum theory in 1900 to explain the observed behavior of black-body radiation. He introduced the concept of energy quantization, suggesting that energy is not continuous but rather exists in discrete packets or "quanta." These energy quanta are now known as photons, the fundamental particles of light.
In Planck's theory, the energy of a photon is directly proportional to its frequency. The equation E = hf represents the relationship between energy (E) and frequency (f), where h is Planck's constant. This equation implies that electromagnetic waves, including light, exhibit both particle-like and wave-like properties. Photons are the quantized packets of energy associated with electromagnetic waves.
Regarding your mention of an EM standing wave that does not expand, it's important to note that electromagnetic waves, including standing waves, can expand and propagate. Standing waves are formed by the interference of two waves of the same frequency traveling in opposite directions. However, Planck's theory focuses on the quantization of energy and the particle-like behavior of photons, rather than the specific nature of standing waves.
The expansion of the electromagnetic field typically refers to the spreading out of the wavefront as it propagates through space. This expansion is a characteristic of waves and occurs in accordance with the principles of wave propagation. However, in the context of Planck's theory, the focus is primarily on the discrete nature of energy and the behavior of photons rather than the detailed properties of expanding electromagnetic fields.