Refractive index ratios

It can be seen from Equation 4, that the scattering coefficient of a paper changes when the ratio of refractive indices at the interfaces, or the specific surface area of the pulp, are changed. Examples of the effects of changing refractive index ratio, as affected by impregnation of a paper with liquids, has been discussed above. 

Figure 2. Predictions of intensity per unit particle volume as a function of particle diameter for three scattering angles given Incident wavelength 514.5 nm and refractive index ratio polystyrene/water of 1.2.

Where, t(X) is the turbidity at the wavelength X, N the number of particles/ml, C the concentration in g/ml, D the particle diameter, f(D) the frequency distribution of particle sizes, p the density of the particles, m is the complex refractive index ratio and Q(a,m) is the Mie overall extinction efficiency. The extinction efficiency is given by... 

It is easy to see from this expression that for some critical angle and a given refractive index ratio, 6 will equal 90° and sin 62 be unity. For all angles greater than the critical angle, d, the incident light will be totally reflected, and we can write... 

The latexes prepared using the water-soluble potassium persulfate or oil-soluble 2,2 -azobls(2-methyl butyronltrlle) Initiators were stable, bluish, and less translucent than the original mlcroemulslons. This change In appearance was attributed to the larger size of the latex particles and the greater refractive Index ratio. The effects of Initiator and monomer concentrations are described below. 

This result simply due to the dielectric boundary conditions imposed on the radiated field of a molecule at the interface. Here 1/Tnr and 1/Tril<1 are the non-radiative and the radiative rates, respectively. The quantity in the brackets accounts for the proximity of the interface at a distance z from the molecule. Algebraic expressions for the weighting functions L zyL and LyfylL are known [114] and depend on z and the refractive index ratio of the two materials that form the interface. The parameter 6t is the angle enclosed between the emission dipole moment and the surface normal. The weighting functions approach unity for z > A. For a molecule adsorbed on a PMMA surface in air, the lifetime should be 2.7 times longer when its emission dipole moment is perpendicular to the interface than when it lies in the surface. Also, the fluorescence quantum yield, defined as = 1 — (t/ rnr), is affected by the location and orientation of the molecule. 

Reflected light covers the entire angular range for refractive index ratios below and above unity. However, a distinct minimum is found for parallel polarized light at the so-called Brewster s angle which is given for a sphere by ... 

The Brewster s angle decreases with increasing refractive index ratio. 

There are different spectrophotometric techniques for analysis of contaminants in biofuels. Simultaneous detection of the absorption spectrum and refractive index ratio with a spectrophotometer for monitoring contaminants in bioethanol has been carried out by Kontturi et al., 2011. Inductively Coupled Plasma Atomic Emission Spectrometry and optical emission spectral analysis with inductively coupled plasma (ICP-OES) have also been used to analyze biodiesel samples for trace metals (ASTM, 2007 ECS, 2006). An ICP-MS instrument fitted with an octopole reaction system (ORS) was used to directly measure the inorganic contents of several biofuel materials. Following sample prepwation by simple... 

Kontturi, V., Hyvmnen, S., Garcia, A., Carmona, R., Yu Murzin, D., Mikkola, J.P. Peiponen, KE. (2011). Simultaneous detection of the absorption spectrum and refractive index ratio with a spectrophotometer monitoring contaminants in bioethanol. Measurement Science and Technology Vol. 22, No. 5, 055803 doi 10.1088/0957-0233/22/5/055803. 

Refractive index Ratio of speed of light in vacuum to speed of Hght in a material. It is a measure of the abihty of a material to refract (bend) a beam of Hght. 

For particles smaller than the wavelength of light used, that is, for the Rayleigh range, the scattering intensity is a strong function of the diameter (sixth power), the wavelength (fourth power) and the complex refractive index ratio as described by the equation ... 

Refractive index Ratio of velocity of light at a given wavelength in air to that in a refractive medium. 

Redox activity Activity pertaining to the gain or loss of electrons Refractive index Ratio of the velocity of light in a vacuum to that in a medium Refractoriness Ability of a dry sand core or mould to withstand the hot liquid metal temperatures... 

It is worth noting at this stage that a refractive index ratio of near unity (e.g., when using an oil-immersion objective), this effect is greatly reduced. Also, the analysis assumes that diffraction effects are negligible and that the (laser) illumination is emanating from a point source or collimated beam. 

The extinction results from the transmission T, which is measured by the detection of the light intensities I and 4, whereby 4 is the intensity of the light beam behind the measurement volume, which is filled exclusively with a continuous phase. I is the intensity of the extinct light beam behind the measurement volume, which is filled with disperse and continuous phase. Cext is the extinction cross section of a particle with a diameter x depending on the wavelength A of the laser and the refractive index ratio m between disperse and continuous phase, is the number concentration of the particles in the spray. is the length of the measurement volume. 

The Fraunhofer theory was the basis for the first (approximating) optical model for particle size measurement. For particles with a diameter dp larger than the wavelength A, Fraunhofer diffraction is often assumed [105]. However, only scattering by opaque particles or particles with a large real refractive index ratio m, i.e., the ratio of the refractive index of scattering particles to that of the fluid. 

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