Refraction and Diffraction

FIGURE 12.2 (See color insert) Refraction Light ray passing a prism. 

The dielectric properties of water and other polar substances are measured by the relative dielectric constant, e, valid in a static electric field. For a propagating EM field, the dielectric constant depends on the frequency of the radiation, for the reasons just given. At light frequencies, the oscillation of dipoles or the vibrations of nuclei are unimportant. Then, as follows from Maxwell s equations, the dielectric constant for a substance is equal to the square of the refractive index (not proven)  

Due to the vibrations and rotations of polar molecules, the relative dielectric constant, in a static or slowly alternating field is higher than n. In water, depending on temperature, e, is roughly equal to 80, but n is only 2. 

---

Explain the meaning of refraction and diffraction. What does a diffraction pattern look like Write down expressions for the radial distribution function. What is the physieal significance of the decline in value of the maximum with increasing distanee from the reference point ... 

Kk ason H. and van der Hilst R. D. (2001) Tomographic imaging of the lowermost mantle with differential times of refracted and diffracted core phases (PKP, P-diff). J. Geophys. Res. 106, 6569-6587. 

If it is no longer possible to differentiate between the phenomena of specular reflection, refraction and diffraction because the diameter d of the sample to be assayed is disproportionately greater than the wavelength X of the light (i.e. the electromagnetic radiation), the reflection must be considered to be diffuse. 

Applying ETCA and the post-peel cream before the flashlamp would change the refractive and diffractive properties of the epidermis, as well as its water content and color. 

Scattering. If the particles are small, which means of the order of the wavelength of light (about 0.5 pm) or smaller, the scattering of light can no longer be separated into reflection, refraction, and diffraction. If the size... 

The diffraction of light waves in such a film can be treated in the same way used by Rayleigh, that is, applying (macroscopic) Maxwell equations with the appropriate boundary conditions at both surfaces. Afterward it was found that the same answers are obtained when the interference of the reflected, refracted, and diffracted waves are treated in an elementary fashion by adding the diffraction of the single surfaces with appropriate phase factors. 

Particles for which a 1 fall into the so-called geometric scattering regime. In this case the scattering can be determined on the basis of the geometrical optics of reflection, refraction, and diffraction. Scattering is strongly dependent on particle shape and orientation... 

If ( ) denotes the geometric optics part and PjY( ) the diffraction part, the total phase function including reflection/refraction and diffraction processes is given by... 

Spectrum A charted band of wavelengths of electromagnetic vibrations obtained by refraction and diffraction. By extension, a measurable range of activity, such as the range of bacteria affected by an antibiotic (antibacterial s.) or the complete range of manifestations of a disease. [EU]... 

On powdered samples, however, the effects of reflection, refraction and diffraction, summarized into scattering, cause severe losses in transmittance. According to theory [26], the scattered intensity Ij from an incident beam with Iq depends on the wavelength A, the volume V and the number of particles per volume unit N and the relative refractive index n, derived for spherical particles is... 

The overall result is that white light is returned from the film to the eyes of the observer, who concludes that the film is white. The greater the difference in refractive indices and the larger the number of particles up to a limiting concentration, the more milky and less transparent the film will appear. Transparent materials can appear white in powder form, because white light is reflected, refracted and diffracted at the many solid-air interfaces. 

Light passes through slits, forming a set of diver ng rays. This apparatus is useful in optics as refraction and diffraction can be better observed when looking at individual rays of light. (Andrew Lambert Photography/Photo Researchers, Inc.)... 

Reflection, Refraction, and Diffraction Very Low Frequency (VLF), Low Frequency (LF), and Medium Frequency (MF)... 

An effective and convenient model equation which has been found to be well suited for combining the effects of wave refraction and diffraction in the coastal region is the two-dimensional elhptic mild slope wave equation first derived by Berkhoff.2... 

Basins are much wider and often larger than flumes, meaning higher construction costs and water usage occur, but the model can be larger and 3D. Waves can be multi-directional and more realistic because the wave transformation mechanisms of wave refraction and diffraction can be simulated. 

Figure 3.1 Schematic representa tion of refraction and diffraction of light by pigment particles...

One of the oldest methods used with molding, but at the same time the least accurate, is cast molding (e.g., injection molding, casting, etc.) [111]. This method is used both for refractive and diffractive lenses. First, a high-accuracy master is fabricated. It is subsequently used to produce large series of microlenses. The method is especially convenient for work with plastic materials transparent in IR, like TPX (polymethylpentane, polymerized dimer of propylene.)... 

Single microlenses with relatively larger dimensions can be efficiently produced mechanically, e.g., using abrasion or polishing. To fabricate both refractive and diffractive microlenses diamond turning is used [124]. One of the methods in this group is microgrinding [125]. 

Diffuse reflection (DR) spectra result from the radiation incident on a powdered sample that is absorbed as it refracts through each particle and is scattered by the combined process of reflection, refraction, and diffraction. That fraction of the incident radiation that reemerges from the upper surface of the sample is said to be diffusely reflected. Because DR spectra result from an absorption process, they have the appearance of transmission spectra (i.e., bands appear in absorption), unlike the case for Fresnel reflection spectra of bulk samples (see Chapter 13). When DR spectra are acquired on Fourier transform spectrometers, the singlebeam spectra of the sample and a nonabsorbing reference are measured separately and ratioed to produce the reflectance spectrum, Rfy). 

Light-scattering is a function of refractive and diffractive mechanisms. The particles are too small to diffract visible light. The refractive index of clay is very close to the refractive index of polymers utilized in packaging. 

M. Hock, W. Doll, G. Kleer, P. Manns, E. Schaffer, G. Spiefi, in Proceedings of Nanocomposite Coating Materials for Low Cost Production of Refractive and Diffractive Optical Components of Inorganic Glasses, Materials Week, Munich, 2002... 

---