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Spatial frequency is a reciprocal length, which can thus be used as a measure of energy, usually of a particle. For example, the reciprocal centimetre, cm −1, is an energy unit equal to the energy of a photon with a wavelength of 1 cm. That energy amounts to approximately 1.24 × 10 −4 eV or 1.986 × 10 −23 J.
The molar absorption coefficient (in units of M −1 cm −1) is directly related to the attenuation cross section (in units of cm 2) via the Avogadro constant N A: [5] σ = ln ( 10 ) 10 3 N A ε ≈ 3.82353216 × 10 − 21 ε . {\displaystyle \sigma =\ln(10){\frac {10^{3}}{N_{\text{A}}}}\varepsilon \approx 3.82353216\times 10^{-21 ...
For example, a wavenumber in inverse centimeters can be converted to a frequency expressed in the unit gigahertz by multiplying by 29.979 2458 cm/ns (the speed of light, in centimeters per nanosecond); [5] conversely, an electromagnetic wave at 29.9792458 GHz has a wavelength of 1 cm in free space.
A graphical or bar scale. A map would also usually give its scale numerically ("1:50,000", for instance, means that one cm on the map represents 50,000cm of real space, which is 500 meters) A bar scale with the nominal scale expressed as "1:600 000", meaning 1 cm on the map corresponds to 600,000 cm=6 km on the ground.
The point D is the harmonic conjugate of C with respect to A and B precisely if the cross-ratio of the quadruple is −1, called the harmonic ratio. The cross-ratio can therefore be regarded as measuring the quadruple's deviation from this ratio; hence the name anharmonic ratio. The cross-ratio is preserved by linear fractional transformations.
The force in the spring is (roughly) the vertical force at the contact patch divided by the motion ratio, and the spring rate is the wheel rate divided by the motion ratio squared. I R = S p r i n g D i s p l a c e m e n t W h e e l D i s p l a c e m e n t . {\displaystyle IR={\frac {SpringDisplacement}{WheelDisplacement}}.}
Thus on an architect's drawing one might read 'one centimeter to one meter', 1:100, 1/100, or 1 / 100 . A bar scale would also normally appear on the drawing. Colon may also be substituted with a specific, slightly raised ratio symbol U+2236 ∶ RATIO (∶), ie. "1∶100".
Since metals can display multiple oxidation numbers, the exact definition of how many "valence electrons" an element should have in elemental form is somewhat arbitrary, but the following table lists the free electron densities given in Ashcroft and Mermin, which were calculated using the formula above based on reasonable assumptions about ...