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  2. Planck's law - Wikipedia

    en.wikipedia.org/wiki/Planck's_law

    In 1905, "Einstein believed that Planck's theory could not be made to agree with the idea of light quanta, a mistake he corrected in 1906." [133] Contrary to Planck's beliefs of the time, Einstein proposed a model and formula whereby light was emitted, absorbed, and propagated in free space in energy quanta localized in points of space. [132]

  3. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    v. t. e. In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift, or negative redshift.

  4. Taylor series - Wikipedia

    en.wikipedia.org/wiki/Taylor_series

    t. e. In mathematics, the Taylor series or Taylor expansion of a function is an infinite sum of terms that are expressed in terms of the function's derivatives at a single point. For most common functions, the function and the sum of its Taylor series are equal near this point.

  5. Density functional theory - Wikipedia

    en.wikipedia.org/wiki/Density_functional_theory

    Density functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of ...

  6. Transmission electron microscopy - Wikipedia

    en.wikipedia.org/wiki/Transmission_electron...

    The polio virus is 30 nm in diameter. [1] Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons ...

  7. Acid dissociation constant - Wikipedia

    en.wikipedia.org/wiki/Acid_dissociation_constant

    Weak. v. t. e. In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ⁠ ⁠) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction. known as dissociation in the context of acid–base reactions.

  8. Platonic solid - Wikipedia

    en.wikipedia.org/wiki/Platonic_solid

    This follows from the spherical excess formula for a spherical polygon and the fact that the vertex figure of the polyhedron {p,q} is a regular q-gon. The solid angle of a face subtended from the center of a platonic solid is equal to the solid angle of a full sphere (4 π steradians) divided by the number of faces. This is equal to the angular ...

  9. Heat equation - Wikipedia

    en.wikipedia.org/wiki/Heat_equation

    Heat equation. Animated plot of the evolution of the temperature in a square metal plate as predicted by the heat equation. The height and redness indicate the temperature at each point. The initial state has a uniformly hot hoof-shaped region (red) surrounded by uniformly cold region (yellow). As time passes the heat diffuses into the cold region.