Model

(noun)

A representation of something difficult or impossible to display directly

Related Terms

Examples of Model in the following topics:

  • The Thomson Model

    • Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model.
    • In this model the atom was also sometimes described to have a "cloud" of positive charge.
    • His conclusions led him to propose the Rutherford model of the atom.
    • A schematic presentation of the plum pudding model of the atom; in Thomson's mathematical model the "corpuscles" (in modern language, electrons) were arranged non-randomly, in rotating rings.
    • Intro to the History of Atomic Theory - The Thomson Model

  • The Bohr Model of the Atom

    • The great Danish physicist Niels Bohr (1885–1962, ) made immediate use of Rutherford's planetary model of the atom.
    • One big puzzle that the planetary-model of atom had was the following.
    • This atom model is disastrous, because it predicts that all atoms are unstable.
    • To overcome this difficulty, Niels Bohr proposed, in 1913, what is now called the Bohr model of the atom.
    • Therefore, his atomic model is called a semiclassical model.

  • The Rutherford Model

    • The Rutherford model is a model of the atom named after Ernest Rutherford.
    • Thomson's so-called "plum pudding model" of the atom was incorrect.
    • Top: Expected results -- alpha particles pass through the plum pudding model of the atom undisturbed.
    • Intro to the History of Atomic Theory - The Rutherford Model
    • Basic diagram of the atomic planetary model; electrons are in green, and the nucleus is in red

  • Models, Theories, and Laws

    • The terms model, theory, and law have exact meanings in relation to their usage in the study of physics.
    • A model is a representation of something that is often too difficult (or impossible) to display directly.
    • While a model's design is justified using experimental information, it is only accurate under limited situations.
    • Physicists use models for a variety of purposes.
    • Some theories include models to help visualize phenomena, whereas others do not.

  • Basic Assumptions of the Bohr Model

    • Bohr explained hydrogen's spectrum successfully by adopting a quantization condition and by introducing the Planck constant in his model.
    • In previous modules, we have seen puzzles from classical atomic theories (e.g., the Rutherford model).
    • Most importantly, classical electrodynamics predicts that an atom described by a (classical) planetary model would be unstable.
    • To explain the puzzle, Bohr proposed what is now called the Bohr model of the atom in 1913.
    • Describe basic assumptions that were applied by Niels Bohr to the planetary model of an atom

  • Problems

    • A reasonable model for the neutrons and protons in a nucleus is that they are confined to a small region.
    • Let's take a one-dimensional model of this.

  • Mass

    • To date, a number of different models have been proposed which advocate different views at the origin of mass.
    • The problem is complicated by the fact that the notion of mass is strongly related to the gravitational interaction but a theory of the latter has not been yet reconciled with the currently popular model of particle physics, known as the Standard Model.

  • Emission

    • If one assumes that the disk radiates locally as a blackbody, the spectrum is simply the sum of the various blackbodies (the so-called multi-temperature disk model).

  • de Broglie and the Bohr Model

    • Bohr's model of electrons traveling in quantized orbits was extended into a more accurate model of electron motion.

  • Problems

    • We will try to model Type-I X-ray bursts using a simple model for the instability.