Polished surfaces reflectivity

A planar polished surface reflects heat radiation in a similar manner with which it reflects light. Rough surfaces reflect energy in a diffuse manner hence radiation is reflected in all directions. A blackbody absorbs all incoming radiation and therefore has no reflection. A perfect blackbody does not exist a near perfect blackbody surface such as soot reflects 5% of the radiation, making it the standard for an ideal radiator. 

The absolute value of and Rq depends on the interval length considered for the measurement. This is illustrated by Figure 3.41 for titanium surfaces polished either mechanically or electrochemically [14]. At small interval length the Rq for the electropolished surface is smaller than for the mechanically polished surface, reflecting the absence of polishing scratches. At an interval length exceeding 300 micrometer... 

Now and then the propellers are caught in the rays of sun, their highly polished surfaces reflect.The sun is striking the windows of the observation deck on the eastward side and sparkling like glittering jewels on the background of black velvet. ... 

For opaque materials, the reflectance p is the complement of the absorptance. The directional distribution of the reflected radiation depends on the material, its degree of roughness or grain size, and, if a metal, its state of oxidation. Polished surfaces of homogeneous materials reflect speciilarly. In contrast, the intensity of the radiation reflected from a perfectly diffuse, or Lambert, surface is independent of direction. The directional distribution of reflectance of many oxidized metals, refractoiy materials, and natural products approximates that of a perfectly diffuse reflector. A better model, adequate for many calculational purposes, is achieved by assuming that the total reflectance p is the sum of diffuse and specular components p i and p. ... 

If the surface of an acrylic sheet, rod or tube is roughened or carved, less light is internally reflected and the material is often rather brighter at these non-polished surfaces. The use of this effect enables highly attractive carvings to be produced. Similarly, lettering cut into sheet, particularly fluorescent sheet, becomes Tit-up and this effect is useful in display signs. 

Tests carried out for particular purposes may make use of other special means to measure the progress of corrosion. For example, changes in the reflectivity of polished surfaces have been used as a sensitive means of following changes in the very early stages of corrosion in laboratory studies. A similar technique has been applied on a practical scale in connection with the direct evaluation of the relative merits of different alloys as used for mirrors in searchlights exposed to corrosive natural atmospheres. 

The reflected light from polished surfaces permits ready distinction between many opaque minerals on the basis of brightness, colour, and anisotropy. This feature is very important in the study of ore minerals and host rocks. Transparent minerals (especially in rocks) are commonly studied by transmitted light. In this case, polarized light is passed through thin sections or through fragments mounted in oil. 

Note These (maceral) constituents can be identified and quantitatively measured by examining thin sections or polished surfaces under a microscope, and reflect the nature of the primordial source material as well as the conditions under which it was deposited. Vitrinites derive from humic gels, wood, bark and cortical tissues eoi lnites are the remains of fungal spores, leaf cuticles, algae, resins and waxes and inertinites comprise unspecified detrital matter, "carbonized" woody tissues and fungal sclerotia and mycelia. 

Optical Properties. The addition of lanthanum oxide to PZT has a rather remarkable effect on the optical transparency, especially when the amount of lanthanum exceeds seven atom percent. Thin polished plates characteristically transmit about 67% of the incident light. When broadband antireflection coatings are applied to the major surfaces, this transmission is increased to greater than 98%. Surface reflection losses are a function of the index of refraction (n = 2.5) of the PLZT. 

The polished surfaces of polycrystalline Al, Cu, Ni and Si(p) and monocrystalline samples of Mo, Si(m) and W were tested to choose the best substrate providing maximal colour contrast. The surface of the substrate was chemically polished to provide mirror reflection. Thin blood smears of the same patient were deposited under the same experimental conditions. After air drying for 10 min, blood samples were placed on the microscope holder. The images were taken by a digital camera. 

Polished aluminum reflects radiation energy in the visible and infrared (IR) energy spectral regions at least as efficiently as in the UV region.1617 This is undesirable in cases where the substrate or the piece being irradiated is heat sensitive. To overcome this, the surface of the reflector is coated with special dielectric coatings... 

Specular reflection is encountered when the reflecting medium is a smooth polished surface. The angle of reflection is identical to the incident angle of the radiation beam. If the surface is IR absorbent, the relative intensity of reflection is less for wavelengths that are absorbed than for wavelengths that are not. Thus, the plot of reflectance R, defined as the fraction of reflected incident radiant energy versus the wavelength (or wavenumber) appears similar to a transmission spectrum for the sample. 

When using optical filters for photometric accuracy measurements, make sure that the filter is placed properly in the sample holder so that the filter is perpendicular to the incident light beam. Problems of reflection from the highly polished surface of the glass filter and interreflection between optical surfaces for metal on quartz filters may occur that affect the readings. 

The physical or petrographic components of coal are defined or described in various ways. In one system, which depends on microscopic observation, the principal components are called exinite, vitrinite, micrinite, and fusinite. Transparency of these in a thin section decreases in that order, whereas reflectance from polished surface increases in the same order. Vitrinite, the major component of most coals, occurs in bands or strands and is usually uniform in appearance, though sometimes shows cell structure exinite consists of the remains of plant spores, pollen, and cuticles with characteristic shape micrinite occurs in very fine granular form or massive structureless, irregular form fusinite shows characteristic fibrous, cellular structure. Semifusinite is transitional between vitrinite and fusinite. On a macroscopic scale, vitrain and... 

Figure I. Dark gray, low reflecting resinite globules in bituminous coalf typical of the material isolated for chemical study relief-polished surface, oil immersion, incident light X 350...

The refractive index of coal can be determined by comparing the reflectance in air with that in cedar oil. A standard test method (ASTM D-2798) covers the microscopic determination of both the mean maximum reflectance and the mean random reflectance measured in oil of polished surfaces of vitrinite and other macerals in coal ranging in rank from lignite to anthracite. This test method can be used to determine the reflectance of other macerals. For vitrinite (various coals), the refractive index usually falls within the range 1.68 (58% carbon coal) to 2.02 (96% carbon coal). 

The topography of cross-sectional surfaces produced by cutting and polishing usually reflects the differences in mechanical properties of its heterogeneities. In general, this is due to the fact that the rate of material removal of hard components like fibres and metals is smaller than that of soft polymeric components. Easily deformable components like rubber inclusions, however, tend to be more compressed rather than abraded and their surfaces are quite often above that of the surrounding material of the final cross-section. 

Since one desires only light reflections from etched facets, the entire surface of the sample should be covered with etch pits. This can be obtained by etching an abraded surface. Fig. 5 shows the results of the action of a preferential etch for germanium on an abraded and on a polished surface. The multitude of pits on a lapped surface raises an interesting question are these pits caused mainly by the multitude of Irregularities produced an the surface by abrasion or by the multitude of mechanically induced dislocations In an attempt to answer this... 

Light (or near-ir and uv radiation) that is incident on opaque minerals is partly absorbed and partly reflected by them. There are two kinds of reflection processes that occurring when light is reflected from a flat polished surface of the mineral (specular reflectance) and that occurring when the light is reflected from the mineral after it has been finely powdered (diffuse reflectance). The latter arises from radiation that has penetrated the crystals (as in an electronic absorption spectrum) and reappeared at the surface after multiple scatterings in this case there will also be a specular component to the reflectance from light that is reflected from the surfaces of the particles. The specular reflectance of a flat polished surface of an opaque mineral measured at normal incidence can be related to the n and k terms of the complex refractive index (N) in which ... 

Light (uv-visible-near-ir radiation) reflected back from a flat, highly polished surface of a solid measured in intensity as a function of varying wavelength. Measurements can be made using plane-polarized light, at normal incidence, and on oriented faces of single crystals... 

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