refractive index | Definition & Equation | omarcafini.info
The optical density of a medium is not the same as its physical density. The physical density of a material refers to the mass/volume ratio. Optical density. Our subject matter experts can help you understand optical density of a medium. which is equal to mass by volume ratio while the optical density is related to The optical density of a material is indicated by the index of refraction value of. The Gladstone-Dale law (specific refraction) and the Drude law (molecular On the relationship between refractive index and density for SiO2 polymorphs v0 of elementary electron oscillators (in energy units, hv) is identified with the band Anderson OL () Optical properties of rock-forming minerals derived from.
The speed of transmitted light is slower in the most optically dense materials than the less dense materials.
Thus, with the increase in the index of refraction value, the optical density increases which decreases the speed of light in that material. It is given by Beer-Lambert Law of Absorbance.
This is especially used in quantitative spectroscopy.
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It shows a linear relationship between absorbance capacity and concentration of an absorber towards the electromagnetic radiation. The Beer-Lambert Law represents the Absorbance A in terms of absorptivity coefficient, the path length, and the concentration of analyte.
In the absorption spectrometer, all the wavelengths of light pass through sample cell which contains solution of a substance and also through the reference cell.
Thus, the intensity of the light is measured which passes through the reference cell in terms of Io and I stands for the intensity of the light which passes through the sample cell.
The optical density is directly proportional to the concentration.
Optical density is measured by spectrophotometer. This is used in the biological research laboratory for measuring the concentration of the substance.
It is especially used to measure the concentration of bacteria in a biological suspension. The amount of scattering light is measured with the use of spectrophotometer.
The visible light passes through suspension of the cell and it scatters the light. The high-level of scattering indicates presence of more bacteria or other material which can be measured in a spectrophotometer. The optical density at a specific wavelength correlates with the various phases of bacterial growth. The measurement of concentration is done at maxima of the absorbance spectra because there is least change in absorbance with change in the wavelength due to zero value of slope of the absorbance spectra.
The measurement of optical density is a common method to quantify various important parameters like concentration of cell, production of biomass or alteration in the cell morphology.
The measurement is based on detecting the concentration of substances by using Beer-Lambert law as the absorbance is directly proportional to the concentration of the absorbing substance of the sample.
Generally, small thickness cuvettes are used for good result approx 10mm thick sample.
If the frequency of the electromagnetic wave does not match the resonant frequency of vibration of the electronthen the energy is reemitted in the form of an electromagnetic wave. This new electromagnetic wave has the same frequency as the original wave and it too will travel at a speed of c through the empty space between atoms.
- Refractive index
- Optical Density and Light Speed
The newly emitted light wave continues to move through the interatomic space until it impinges upon a neighboring particle. The energy is absorbed by this new particle and sets the electrons of its atoms into vibration motion. And once more, if there is no match between the frequency of the electromagnetic wave and the resonant frequency of the electron, the energy is reemitted in the form of a new electromagnetic wave.
The cycle of absorption and reemission continues as the energy is transported from particle to particle through the bulk of a medium.
Every photon bundle of electromagnetic energy travels between the interatomic void at a speed of c; yet time delay involved in the process of being absorbed and reemitted by the atoms of the material lowers the net speed of transport from one end of the medium to the other.
Optical Density and the Index of Refraction Like any wave, the speed of a light wave is dependent upon the properties of the medium. In the case of an electromagnetic wave, the speed of the wave depends upon the optical density of that material. The optical density of a medium is not the same as its physical density.
How does optical density relate to mass density and refractive index?
The optical density of a material relates to the sluggish tendency of the atoms of a material to maintain the absorbed energy of an electromagnetic wave in the form of vibrating electrons before reemitting it as a new electromagnetic disturbance.
The more optically dense that a material is, the slower that a wave will move through the material. One indicator of the optical density of a material is the index of refraction value of the material.
Index of refraction values represented by the symbol n are numerical index values that are expressed relative to the speed of light in a vacuum. The index of refraction value of a material is a number that indicates the number of times slower that a light wave would be in that material than it is in a vacuum. A vacuum is given an n value of 1.