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How did the Theory of Quantum Mechanics postulated? Who are the scientist involved to examine the Theory of Quantum Mechanics to prove the reality?
Now we continue with the second part of our blog on quantum mechanics. Those who have missed our first blog can read it from Here. It will help to connect with this second part of the blog discussing details about the postulation and examination of quantum Mechanics in a chronological way to prove the reality. In the words of Niels Bohr:
“The very nature of the quantum theory ... forces us to regard the space-time coordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and description, respectively”.
In the 17th and 18th centuries scientific examined the wave nature of light when scientists such as Robert Hooke, Christiaan Huygens and Leonhard Euler contemplated a wave theory of light based on experimental observations. In the year 1803, an English polymath named Thomas Young, performed the famous double-slit experiment that he later described in a paper titled “On the nature of light and colours”. This experiment played a important role in the general approval of the wave theory of light.
In the year 1838, Michael Faraday discovered the cathode rays. These scientific analysis were followed by the 1859 when Gustav Kirchhoff proposed the black-body radiation problem. In the year 1877 Ludwig Boltzmann suggested the energy states of a physical system can be discrete. In the year 1900, Max Planck hypothesized the quantum theory and Planck's hypothesis states that energy is radiated and absorbed in discrete "quanta" (or energy packets) precisely matched the observed patterns of black-body radiation. In the year 1896, Wilhelm Wien empirically resolved a distribution law of black-body radiation, and it is named as Wien's law in his honour. Ludwig Boltzmann individually arrived at this conclusion by considerations of Maxwell's equations. However, it was valid only at high frequencies and underestimated the radiance at low frequencies. Later, Planck rectified this model using Boltzmann's statistical interpretation of thermodynamics and proposed what is now called Planck's law, which concluded to the concept of modern quantum mechanics. Following Max Planck's solution in the year 1900 to the black-body radiation problem (reported 1859), Albert Einstein offered a quantum-based theory to explain the photoelectric effect (1905, reported 1887). Around 1900-1910, the atomic theory and the corpuscular theory of light first came to be widely accepted as scientific fact; these latter theories can be viewed as quantum theories of matter and electromagnetic radiation, respectively. Among the first to study quantum phenomena in nature were Arthur Compton, C. V. Raman, and Pieter Zeeman, each of whom has a quantum effect named after him. Robert Andrews Millikan studied the photoelectric effect experimentally, and Albert Einstein developed a theory for it. At the same time, Ernest Rutherford experimentally discovered the nuclear model of the atom, for which Niels Bohr developed his theory of the atomic structure, which was later confirmed by the experiments of Henry Moseley. In 1913, Peter Debye extended Niels Bohr's theory of atomic structure, introducing elliptical orbits, a concept also introduced by Arnold Sommerfeld. This phase is popularly known as old quantum theory.
What is Photoelectric Effect?
In 1887, Heinrich Hertz observed that when light with sufficient frequency hits a metallic surface, it emits electrons. In 1902, Philipp Lenard discovered that the maximum possible energy of an ejected electron is related to the frequency of the light, not to its intensity: if the frequency is too low, no electrons are ejected regardless of the intensity. Strong beams of light toward the red end of the spectrum might produce no electrical potential at all, while weak beams of light toward the violet end of the spectrum would produce higher and higher voltages. The lowest frequency of light that can cause electrons to be emitted, called the threshold frequency, is different for different metals. This observation is at odds with classical electromagnetism, which predicts that the electron's energy should be proportional to the intensity of the radiation. So when physicists first discovered devices exhibiting the photoelectric effect, they initially expected that a higher intensity of light would produce a higher voltage from the photoelectric device. Einstein explained the effect by postulating that a beam of light is a stream of particles ("photons") and that, if the beam is of frequency f, then each photon has an energy equal to hf. An electron is likely to be struck only by a single photon, which imparts at most an energy hf to the electron. Therefore, the intensity of the beam has no effect and only its frequency determines the maximum energy that can be imparted to the electron.
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