Max Planck is often considered the founder of quantum theory, but he is not typically referred to as the founder of quantum mechanics or quantum electrodynamics. This distinction is primarily due to the development of these theories by other physicists who built upon Planck's initial contributions.
Max Planck's groundbreaking work in the early 20th century led to the formulation of the concept of quantization. In 1900, he proposed that energy is quantized in discrete packets called "quanta" or "energy elements," which later became known as "photons." This marked a fundamental departure from classical physics, where energy was thought to be continuous. Planck's work laid the foundation for quantum theory.
However, the development of quantum mechanics as a complete theory was carried forward by several other scientists. Albert Einstein, in 1905, explained the photoelectric effect using the concept of photons, which contributed to the understanding of light as both a particle and a wave. This work was further expanded upon by other scientists, including Niels Bohr, Werner Heisenberg, Erwin Schrödinger, and others, who developed the mathematical formalism and principles of quantum mechanics.
Quantum electrodynamics (QED) is a more specialized field within quantum theory that specifically deals with the behavior of electromagnetic interactions at the quantum level. While Planck's work on quantization and the existence of photons laid the foundation for understanding the particle-like nature of light, the development of QED as a comprehensive theory was primarily accomplished by Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga in the late 1940s. They formulated the mathematical framework and introduced the concept of renormalization to address the challenges of calculating and interpreting quantum interactions involving photons and charged particles.
Therefore, while Max Planck's work was crucial in establishing the concept of quantization and the existence of photons, the subsequent development and formulation of quantum mechanics and quantum electrodynamics as complete theories involved contributions from numerous other physicists. As a result, Planck is recognized as a foundational figure in quantum theory, but the specific titles of "founder of quantum mechanics" and "founder of quantum electrodynamics" are generally attributed to other scientists who made significant advancements in those respective fields.