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The relationship between energy and wavelength is determined by the Planck-Einstein relation E = h f = h c λ {\displaystyle E=hf={\frac {hc}{\lambda }}} where E is the energy of the quantum ( photon ), f is the frequency of the light wave, h is the Planck constant , λ is the wavelength and c is the speed of light .
A common misconception occurs between phase velocity and group velocity (analogous to centres of mass and gravity). They happen to be equal in non-dispersive media. In dispersive media the phase velocity is not necessarily the same as the group velocity. The phase velocity varies with frequency.
The de Broglie wavelength is the wavelength, λ, associated with a particle with momentum p through the Planck constant, h: =. Wave-like behavior of matter has been experimentally demonstrated, first for electrons in 1927 and for other elementary particles , neutral atoms and molecules in the years since.
The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.
Wavenumber, as used in spectroscopy and most chemistry fields, is defined as the number of wavelengths per unit distance, typically centimeters (cm −1): ~ =, where λ is the wavelength. It is sometimes called the "spectroscopic wavenumber". [1]
The relationship between the momentum and position space wave functions, for instance, describing the same state is the Fourier transform. Each choice of representation should be thought of as specifying a unique function space in which wave functions corresponding to that choice of representation lives.
A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The typical vibrational frequencies range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1 and wavelengths of approximately 30 to 3 μm.
This could only be applied to hydrogen-like atoms. In 1908 Ritz derived a relationship that could be applied to all atoms which he calculated prior to the first 1913 quantum atom and his ideas are based on classical mechanics. [10] This principle, the Rydberg–Ritz combination principle, is used today in identifying the transition lines of atoms.