and the Nature of Light
Barry R. Masters
Einstein’s genius lay in his ability to bridge the gap between radiation in
space and radiation-matter interactions. He explained the interaction between
light and matter by the absorption and emission of light quanta, thereby
explaining several perplexing physical phenomena.
lbert Einstein was one of the foremost scientists in a century dominated by
science. His work influenced our understanding of the physics of the universe,
modern electronics and the quantum nature of reality. Perhaps it was his
boundless imagination that enabled him to have such a broad reach.
Indeed, throughout his life and career, Einstein pursued independent thought. In 1901, he
wrote: “German worship for authority … is the greatest enemy of truth.” In Einstein’s Auto-
biographical Notes, which he wrote at age 67, he noted his “suspicion against every kind of
authority…and [that] attitude which has never left me.” This theme is recounted in another
Einstein quote from 1925: “The pursuit of knowledge for its own sake, an almost fanatical
love of justice, and the desire for personal independence—these are the features of the Jewish
tradition which makes me thank the stars that I belong to it.”
While it was Einstein’s relativity theory that put him on the world’s stage, he made several
critical contributions to the field of optics. Between 1905 and 1916, he put forth the light
quantum hypothesis, demonstrated the wave-particle duality of light, and proposed the con-
cept of stimulated emission—an idea that took 40 years to be proven in the form of the laser.
Einstein’s light quantum and the photoelectric effect
In his 1905 publication, “On a Heuristic Viewpoint Concerning the Production and Transformation of Light,” Einstein used Boltzmann’s statistics to postulate that the entropy of
blackbody radiation can be considered as a gas of independent “quanta of energy,” with each
quantum proportional to the frequency of the corresponding wave. His concept of discontinuous energy in space contradicted Maxwell’s widely accepted continuous wave theory.
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