What is Quantum basics: Definition and 83 Discussions

Quantum mechanics is the study of very small things. It explains the behavior of matter and its interactions with energy on the scale of atomic and subatomic particles. By contrast, classical physics explains matter and energy only on a scale familiar to human experience, including the behavior of astronomical bodies such as the Moon. Classical physics is still used in much of modern science and technology. However, towards the end of the 19th century, scientists discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain. The desire to resolve inconsistencies between observed phenomena and classical theory led to two major revolutions in physics that created a shift in the original scientific paradigm: the theory of relativity and the development of quantum mechanics. This article describes how physicists discovered the limitations of classical physics and developed the main concepts of the quantum theory that replaced it in the early decades of the 20th century. It describes these concepts in roughly the order in which they were first discovered. For a more complete history of the subject, see History of quantum mechanics.
Light behaves in some aspects like particles and in other aspects like waves. Matter—the "stuff" of the universe consisting of particles such as electrons and atoms—exhibits wavelike behavior too. Some light sources, such as neon lights, give off only certain specific frequencies of light, a small set of distinct pure colors determined by neon's atomic structure. Quantum mechanics shows that light, along with all other forms of electromagnetic radiation, comes in discrete units, called photons, and predicts its spectral energies (corresponding to pure colors), and the intensities of its light beams. A single photon is a quantum, or smallest observable particle, of the electromagnetic field. A partial photon is never experimentally observed. More broadly, quantum mechanics shows that many properties of objects, such as position, speed, and angular momentum, that appeared continuous in the zoomed-out view of classical mechanics, turn out to be (in the very tiny, zoomed-in scale of quantum mechanics) quantized. Such properties of elementary particles are required to take on one of a set of small, discrete allowable values, and since the gap between these values is also small, the discontinuities are only apparent at very tiny (atomic) scales.
Many aspects of quantum mechanics are counterintuitive and can seem paradoxical because they describe behavior quite different from that seen at larger scales. In the words of quantum physicist Richard Feynman, quantum mechanics deals with "nature as She is—absurd".For example, the uncertainty principle of quantum mechanics means that the more closely one pins down one measurement (such as the position of a particle), the less accurate another complementary measurement pertaining to the same particle (such as its speed) must become.
Another example is entanglement, in which a measurement of any two-valued state of a particle (such as light polarized up or down) made on either of two "entangled" particles that are very far apart causes a subsequent measurement on the other particle to always be the other of the two values (such as polarized in the opposite direction).
A final example is superfluidity, in which a container of liquid helium, cooled down to near absolute zero in temperature spontaneously flows (slowly) up and over the opening of its container, against the force of gravity.

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  2. Frigorifico9

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  3. golya

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  7. James1238765

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  8. lindberg

    B What is a non-local Hamiltonian?

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  9. D

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  12. Z

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  13. S

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  14. Q

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  15. Mutatis

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  16. P

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  17. L

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  18. D

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  19. J

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  20. Safder Aree

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  22. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 1: Black Body Radiation I

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 1: Black Body Radiation I

    All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
  23. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 2: Black Body Radiation II

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 2: Black Body Radiation II

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  24. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 3: Black Body Radiation III

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 3: Black Body Radiation III

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  25. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 6: Black Body Radiation VI

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 6: Black Body Radiation VI

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  26. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 7: Black Body Radiation VII

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 7: Black Body Radiation VII

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  27. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 8: Radiation as a collection of particles called photons

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 8: Radiation as a collection of particles called photons

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  28. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 9: Quantum Hypothesis and specific heat of solids

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 9: Quantum Hypothesis and specific heat of solids

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  29. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 10: Bohr's Model of hydrogen spectrum

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 10: Bohr's Model of hydrogen spectrum

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  30. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 11: Wilson Sommerfeld quantum condition I

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 11: Wilson Sommerfeld quantum condition I

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  31. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 12: Wilson Sommerfeld quantum condition II

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 12: Wilson Sommerfeld quantum condition II

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  32. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 13: Wilson Sommerfeld quantum condition III

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 13: Wilson Sommerfeld quantum condition III

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  33. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 14: Quantum conditions and atomic structure

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 14: Quantum conditions and atomic structure

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  34. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 15: Eienstien's A and B coefficients

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 15: Eienstien's A and B coefficients

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  35. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 16: Stimulated emission and amplification of light in a LASER

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 16: Stimulated emission and amplification of light in a LASER

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  36. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 17: Brief description of a LASER

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 17: Brief description of a LASER

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  37. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 18: Introduction to the correspondence principle

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 18: Introduction to the correspondence principle

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  38. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 19: General nature of the correspondence principle

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 19: General nature of the correspondence principle

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  39. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 20: Selection rules (for transitions) through the correspondence principle

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 20: Selection rules (for transitions) through the correspondence principle

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  40. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 21: Applications of the correspondence principle

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 21: Applications of the correspondence principle

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  41. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 22: Heisenberg's formulations of quantum mechanics I

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 22: Heisenberg's formulations of quantum mechanics I

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  42. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 23: Heisenberg's formulations of quantum mechanics II

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 23: Heisenberg's formulations of quantum mechanics II

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  43. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 24: Heisenberg's formulations of quantum mechanics III

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 24: Heisenberg's formulations of quantum mechanics III

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  44. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 25: Brief introduction to matrix mechanics

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 25: Brief introduction to matrix mechanics

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  45. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 26: Introduction to waves and wave equation

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 26: Introduction to waves and wave equation

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  46. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 27: Sationary waves eigen values and eigen functions

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 27: Sationary waves eigen values and eigen functions

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  47. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 28: Matter waves and their experimental detection

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 28: Matter waves and their experimental detection

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  48. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 29: Representing a moving particle by a wave packet

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 29: Representing a moving particle by a wave packet

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  49. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 30: Stationary-state Schrodinger equation

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 30: Stationary-state Schrodinger equation

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  50. Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 31: Solution of the stationary-state Schrodinger equation for a SHO

    Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 31: Solution of the stationary-state Schrodinger equation for a SHO

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