Explain 5 theories related to Quantum Mechanics
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Answer:
quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics describing the properties of nature on an atomic scale.[2]
Classical physics, the description of physics that existed before the formulation of the theory of relativity and of quantum mechanics, describes many aspects of nature at ordinary (macroscopic) scale. Quantum mechanics explains the aspects of nature at ordinary (macroscopic) scales but extends this description to the small (atomic and subatomic) scales. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale.[3] Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values (quantization), objects have characteristics of both particles and waves (wave-particle duality), and there are limits to how accurately the value of a physical quantity can be predicted prior to its measurement, given a complete set of initial conditions (the uncertainty principle).[note 1]
Quantum mechanics arose gradually, from theories to explain observations which could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and the correspondence between energy and frequency in Albert Einstein's 1905 paper which explained the photoelectric effect. Early quantum theory was profoundly re-conceived in the mid-1920s by Erwin Schrödinger, Werner Heisenberg, Max Born and others. The modern theory is formulated in various specially developed mathematical formalisms. In one of them, a mathematical function, the wave function, provides information about the probability amplitude of energy, momentum, and other physical properties of a particle.
Quantum theory (otherwise known as quantum physics or quantum mechanics) is one of the two main planks of modern physics, along with general relativity, and between them the two theories claim to explain virtually everything about the universe. General relativity gives us our picture of the very big (space-time and gravity), while quantum theory gives us our picture of the very small (atoms and their constituents).
Technically, quantum theory is actually the theory of any objects isolated from their surroundings but, because it is very difficult to isolate large objects from their environments, it essentially becomes a theory of the microscopic world of atoms and sub-atomic particles. This is especially true for those parts of the theory which rely on the absolute indistinguishability of fundamental particles, an indistinguishability which is impossible to find in the everyday world of composite, large-scale objects.
Quantum theory is used in a huge variety of applications in everyday life, including lasers, CDs, DVDs, solar cells, fiber-optics, digital cameras, photocopiers, bar-code readers, fluorescent lights, LED lights, computer screens, transistors, semi-conductors, super-conductors, spectroscopy, MRI scanners, etc, etc. By some estimates, over 25% of the GDP of developed countries is directly based on quantum physics. It even explains the nuclear fusion processes taking place inside stars.
However, some of its findings and principles are distinctly counter-intuitive and fiendishly difficult to explain in simple language, without resorting to complex mathematics way beyond the comfort level of most people (myself included!). This situation is not helped by the fact that the “theory” is largely a patchwork of fragments accrued over the last century or so, that some elements of it are still not well understood by the scientists themselves, and that some of the bizarre behavior it predicts appears to fly in face of what we have come to think of as common sense.