How does optical density relate to mass density and refractive index? | Physics Forums
The inter-dependence between refractive index and density of inorganic u and v are approximately equal to , and M is the averaged atomic mass of a. centration by volume (m/V) is equal to the concentration by mass (m/m) multiplied by a density factor. These relationships permit the The residual standard deviation was 0 refractive index unit. The differences between. The considerations are based on the Lorentz electron theory of solids. (or eigenfrequency) v0 of elementary electron oscillators (in energy units, hv) is identified with the SiO2 Refractive Index Refraction Ionization Potential Atomic Weight.
RD remains nearly constant with changes of temperature and pressure by virtue of the density factor, which is a function of temperature and pressure and. The refractive index increases as pressure increases, due to the resulting increase in density. This effect is not as significant with liquids as with gases.
Lastly, the refractive index decreases as the wave length increases.
For this reason, one cannot compare indices measured at different wavelengths of light. Estimation Method As the refractive index estimation scheme, following scheme is very popular.
I already expand this scheme for Halogen-containing functional groups. I validated this scheme for data base compounds. Maybe the measurement was done with high pressure.
How does optical density relate to mass density and refractive index?
For other compounds, the accuracy is high enough with group contribution method. The temperature dependency of refractive index is not so high and too little experimental data are available for temperature dependency. This type of estimation scheme is similar with density, so if the molecular size become larger that does not mean larger refractive index. But some of the estimation schemes use plain group contribution method to predict Refractive Index. Such scheme answer very bad result for larger molecule.
Almost all solids and liquids have refractive indices above 1. Aerogel is a very low density solid that can be produced with refractive index in the range from 1. Most plastics have refractive indices in the range from 1.
Moreover, topological insulator material are transparent when they have nanoscale thickness. These excellent properties make them a type of significant materials for infrared optics.
The refractive index measures the phase velocity of light, which does not carry information. This can occur close to resonance frequenciesfor absorbing media, in plasmasand for X-rays. In the X-ray regime the refractive indices are lower than but very close to 1 exceptions close to some resonance frequencies.
Since the refractive index of the ionosphere a plasmais less than unity, electromagnetic waves propagating through the plasma are bent "away from the normal" see Geometric optics allowing the radio wave to be refracted back toward earth, thus enabling long-distance radio communications.
See also Radio Propagation and Skywave. Negative index metamaterials A split-ring resonator array arranged to produce a negative index of refraction for microwaves Recent research has also demonstrated the existence of materials with a negative refractive index, which can occur if permittivity and permeability have simultaneous negative values.
The resulting negative refraction i. Ewald—Oseen extinction theorem At the atomic scale, an electromagnetic wave's phase velocity is slowed in a material because the electric field creates a disturbance in the charges of each atom primarily the electrons proportional to the electric susceptibility of the medium.
Estimation of Refractive Index
Similarly, the magnetic field creates a disturbance proportional to the magnetic susceptibility. As the electromagnetic fields oscillate in the wave, the charges in the material will be "shaken" back and forth at the same frequency.
The light wave traveling in the medium is the macroscopic superposition sum of all such contributions in the material: This wave is typically a wave with the same frequency but shorter wavelength than the original, leading to a slowing of the wave's phase velocity.
Most of the radiation from oscillating material charges will modify the incoming wave, changing its velocity.
However, some net energy will be radiated in other directions or even at other frequencies see scattering. Depending on the relative phase of the original driving wave and the waves radiated by the charge motion, there are several possibilities: