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In 1905, Albert Einstein published a paper advancing the hypothesis that light energy is carried in discrete quantized packets to explain experimental data from the photoelectric effect. Einstein theorized that the energy in each quantum of light was equal to the frequency of light multiplied by a constant, later called the Planck constant. A ...
Einstein's explanation of the photoelectric effect extended the quantum theory which Max Planck had developed in his successful explanation of black-body radiation. Despite the greater fame achieved by his other works, such as that on special relativity, it was his work on the photoelectric effect that won him his Nobel Prize in 1921. [9]
The energy content of this volume element at 5 km from the station is 2.1 × 10 −10 × 0.109 = 2.3 × 10 −11 J, which amounts to 3.4 × 10 14 photons per (). Since 3.4 × 10 14 > 1, quantum effects do not play a role. The waves emitted by this station are well-described by the classical limit and quantum mechanics is not needed.
The photoelectric effect: Einstein explained this in 1905 (and later received a Nobel prize for it) using the concept of photons, particles of light with quantized energy. Robert Millikan's oil-drop experiment, which showed that electric charge occurs as quanta (whole units). (1909)
The notions of light as a particle resurfaced in the 20th century with the photoelectric effect. In 1905, Albert Einstein explained this effect by introducing the concept of light quanta or photons. Quantum particles are considered to have wave–particle duality.
The phenomenon was called the Hallwachs effect (German: Hallwachs-Effekt), now called the photoelectric effect. The investigation of the photoelectric effect laid the foundation for the development of the photoelectric cell, photo electricity and Albert Einstein's quantum light hypothesis. [1]
The first person to correctly predict the phenomenon of spontaneous emission was Albert Einstein in a series of papers starting in 1916, culminating in what is now called the Einstein A Coefficient. [1] [2] Einstein's quantum theory of radiation anticipated ideas later expressed in quantum electrodynamics and quantum optics by several decades. [3]
The process is described by the Einstein coefficient (m 3 J −1 s −2), which gives the probability per unit time per unit energy density of the radiation field per unit frequency that an electron in state 1 with energy will absorb a photon with an energy E 2 − E 1 = hν and jump to state 2 with energy .