Polarization

2011 ◽  
Author(s):  
Sönke Johnsen
Keyword(s):  
Polarized Light ◽  
Coherent Scattering ◽  
Single Scattering ◽  
The Other ◽  
Butterfly Wings

This chapter examines polarization. As with radiometry, polarization can be a confusing topic. Unfortunately, unlike radiometry, its complexity is not primarily due to confusing units. The physics of polarized light is genuinely tricky. This is another subfield of optics that is made easier by thinking of light as a wave. Polarized light in nature is a scattering phenomenon. However, not all scattering is equally effective at polarizing light. Two kinds work best. The first is single scattering by particles much smaller than a wavelength of light. The other way in which scattering can create polarized light is via coherent scattering—in particular, reflection from smooth substances such as glass, water, and many leaves or structurally colored objects like iridescent butterfly wings.

scholarly journals Dermoscopic aspect of verrucous epidermal nevi: New findings

2019 ◽  
Author(s):  
ÖMER FARUK ELMAS ◽  
NECMETTİN AKDENİZ
Keyword(s):  
Polarized Light ◽  
Diagnostic Methods ◽  
The Other ◽  
Diagnostic Process ◽  
Fine Scale ◽  
Epidermal Nevus ◽  
Clinical Interpretation ◽  
New Findings ◽  
Clinical Variants ◽  
Histopathological Investigation

Background and Aim: Verrucous epidermal nevi are cutaneous hamartomas having many clinical variants. Dermoscopic features of verrucous epidermal nevus have rarely been investigated. We aimed to identify dermoscopic findings of the entity which will facilitate the diagnostic process by reducing the use of invasive diagnostic methods. Material and Methods: The study included the patients with histopathologically approved verrucous epidermal nevus. Clinical, dermoscopic and histopathological features of the patients were retrospectively reviewed and the findings identified were recorded. Dermoscopic examination was performed with a polarized-light handheld dermoscope with 10-fold magnification. Results: The most common dermoscopic features were thick brown circles, thick brown branched lines and terminal hairs. The most common vessel pattern was dotted vessels. Branched thick brown lines, brown globules, brown dots forming lines, serpiginous brown dots, white and brown exophytic papillary structures, fine scale, thick adherent scale and cerebriform structures were the other findings. Conclusion: We observed many vascular and non-vascular dermoscopic findings which have not been described previously for the entity. Dermoscopic examination of the verrucous epidermal nevi may lead more reliable clinical interpretation and thus it may reduce the need for histopathological investigation. Keywords: dermoscopy, large brown circles, verrucous epidermal nevus

scholarly journals Exploiting the Binocular Head in Polarized Light Microscopy

1994 ◽  
Vol 2 (4) ◽  
pp. 16-16
Author(s):  
Walter C. McCrone
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
The Other ◽  
Monocular Viewing ◽  
Area Of Interest

Having been brought up on monocular microscopes I find the omnipresent binocular systems a luxury. To support this viewpoint I'd like to suggest some benefits you may not have considered.Because I'm used to monocular viewing I sometimes use two different oculars, say 10X and 25X, in order to scan quickly to find an area of interest and then to examine the detail with higher magnification. Occasionally I use both oculars simultaneously and “concentrate” on either image to the exclusion of the other. A better way is to set the interocular distance at the extreme setting most different from your own interocular distance. By moving your head about a centimeter either way you can use either ocular.

An in vitro Evaluation of Artificial Caries-like Lesions on Restored Overdenture Abutments

1988 ◽  
Vol 67 (3) ◽  
pp. 582-584 ◽  
Author(s):  
P.P. Kambhu ◽  
R.L. Ettinger ◽  
J.S. Wefel
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
The Other ◽  
Type Ii ◽  
Restorative Materials ◽  
Abutment Teeth ◽  
The Mean ◽  
Materials Used

An acidified dialyzed gelatin gel system was used to determine the caries resistance of a variety of restorative materials used to obturate the canal orifice of overdenture abutment teeth. The restorative materials used were Tytin, Tytin + Copalite, P30 + Scotchbond, Fuji Ionomer-Type II, and Miracle Mix. Polarized light microscopy and microradiography were used to examine the caries-like lesions adjacent to the restorations. The lesions formed in the Fuji Ionomer-Type II and Miracle Mix groups appeared arrested at the wall adjacent to the restoration, and did not penetrate apically down the wall as did those associated with the other restorative materials. The mean depths of lesions adjacent to Fuji Ionomer-Type II and Miracle Mix restorations were significantly less than those of Tytin, Tytin + Copalite, or P30 + Scotchbond.

scholarly journals Inhibition of Demineralization at Restoration Margins of Z100 and Tetric EvoCeram Bulk Fill in Dentin and Enamel

2019 ◽  
Vol 6 (2) ◽  
pp. 36
Author(s):  
Cristina Leon-Pineda ◽  
Kevin Donly
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
In Vitro Study ◽  
The Other ◽  
Solution Ph ◽  
Class V ◽  
The Mean ◽  
Student’S T ◽  
Student’S T Test

Recurrent caries is still considered the main reason restorations need to be replaced. There are different materials available now that promise to reduce the possibility of recurrent caries by releasing fluoride and inhibiting restoration marginal caries. The purpose of this in vitro study was to evaluate the demineralization inhibition potential of a non-fluoride-releasing resin (Z100TM 3M, St. Paul, MN, USA) and a glass containing resin-based composite (Tetric EvoCeram Bulk Fill, Ivoclar/Vivadent AG, Schaan, Liechtenstein), which contains fluoride. Class V preparations were placed on 22 premolars; the gingival margin was below the cementoenamel junction and the occlusal margin was placed above the cemento-enamel junction. Ten teeth were randomly selected to be restored with Z100 while the other 10 were restored with Tetric EvoCeram Bulk Fill. Both groups were restored following manufacturer’s instructions. All teeth had an acid resistant varnish placed within one millimeter of the preparation margins. Both groups were placed in artificial caries challenge solution (pH 4.4). At the end of the 4 days; 100 µm buccolingual sections were obtained for each tooth; these were photographed under polarized light microscopy and the demineralized areas adjacent to the restorations were measured and quantified. The mean (±S.D.) area (µm2) of demineralization from the occlusal margin (enamel) and dentin margin were: Z100 2781.889 ± 1045.213; 3960.455 ± 705.964 and for Tetric EvoCeram Bulk Fill 1541.545 ± 1167.027; 3027.600 ± 512.078. Student’s t-test indicated that there was significantly less enamel and dentin demineralization adjacent to Tetric EvoCeram Bulk Fill compared to Z100; there was significantly less demineralization in enamel compared to dentin in both Tetric EvoCeral Bulk Fill and Z100. Tetric EvoCeram Bulk Fill performed better inhibiting demineralization at restoration margins when compared to Z100 and provided better demineralization inhibition in enamel than cementum/dentin.

II. Note on the separation of the isomeric amylic alcohols formed by fermentation

1869 ◽  
Vol 17 ◽  
pp. 308-309
Keyword(s):  
Polarized Light ◽  
The Other ◽  
Detailed Account ◽  
The One

At present we are acquainted with two amylic alcohols formed by fermentation. They were discovered by Pasteur, who observed that different specimens of amylic alcohol caused a ray of polarized light to rotate to dif­ferent degrees. He succeeded in devising a separation of these alcohols, which consisted in converting them into sulphamylates of barium and re­crystallizing these salts. The one alcohol is without action on polarized light, and the other rotates it. This method of separation is beset with great practical difficulties, and has, we believe, only once been repeated, viz. by Mr. Pedler. He gives no detailed account of the separation, but gives some of the leading properties of the alcohols. He found that the rotating alcohol caused a ray of polarized light to rotate 17° with a column of 500 millims. of liquid. The following are some examples of the rotations effected by eleven different samples of amylic alcohol in a column of 385 millims. For compa­rison with Pedler’s number, the observed numbers have been reduced in the second column to observations on 500 millims.

scholarly journals On the laws which regulate the absorption of polarized light by doubly refracting crystals. By David Brewster, LL. D. F. R. S. Lond. and Edinb. In a letter addressed to the Right Hon. Sir Joseph Banks, Bart. G. C. B. P. R. S

1833 ◽  
Vol 2 ◽  
pp. 104-105
Keyword(s):  
Polarized Light ◽  
The Other ◽  
Double Refraction ◽  
Pink Colour ◽  
The One ◽  
The Right ◽  
Number Of Particles

In examining the polarizing structure of acetate of copper, the author’s attention was drawn to certain changes of colour exhibited by its crystal, when exposed in different positions to polarized light; and as these were independent of the thickness of the plate, and of any analysis of the transmitted pencil, he was induced to regard them as a new affection of light, ascribable to the absorption of the homogeneous tints forming the compound colour of the crystal. Dr. Brewster, therefore, collected a variety of coloured crystals, with a view to examine the phenomena which they presented, when cut at different angles with the axis, and when exposed in different positions to polarized light. The details of this examination are next given; and as the property of transparent bodies, by which they detain and assimilate to their own substance a portion of the rays which penetrate them while the rest are freely transmitted, is related to the axes of double refraction, the author first describes the phenomena presented by crystals of one axis, and then explains the modifications which they undergo when the number of axes is increased. It appears from these investigations that the colouring particles of crystals, instead of being indiscriminately dispersed throughout their mass, have an arrangement related to the ordinary and extraordinary forces which they exert upon light. In some cases, the extraordinary medium appeared to be tinged with the same kind and number of colouring particles as the ordinary medium; but in other cases, in the same mineral, the extraordinary medium was either tinged with a different number of particles of the same colour, or with a colouring matter entirely different from that of the ordinary medium. In some specimens of topaz the colouring matter of the one medium was more easily discharged by heat than that of the other, one of the pencils being yellow and the other pink : hence it is a mistake to suppose that in converting yellow topazes into pink by heat, the former colour is changed into the latter; the fact being, that the yellow is discharged by heat, thus leaving the pink unimpaired. Hence it may be ascertained beforehand whether a topaz will receive a pink colour by heat; for if that colour exist in one of its images, seen by exposing it to a polarized ray, we may predict the success of the experiment.

A note on the enhancement of J values in optically thick scattering atmospheres

1991 ◽  
Vol 69 (8-9) ◽  
pp. 1166-1174 ◽  
Author(s):  
Jacek W. Kaminski ◽  
John C. McConnell
Keyword(s):  
Multiple Scattering ◽  
Rayleigh Scattering ◽  
Large Fraction ◽  
Coherent Scattering ◽  
Single Scattering ◽  
Average Density ◽  
Infinite Medium ◽  
Scattering Medium ◽  
Surface Reflection ◽  
Thick Medium

In a planetary atmosphere the J value is determined by the angular-averaged radiance, or the average density of photons in an element of volume. The average density may be enhanced by multiple scattering of photons in a conservative, or near-conservative scattering atmosphere. We show that in a conservative semi-infinite medium this enhancement will be a factor of 5, for optical depths greater than about 20 for coherent scattering. We investigate the modification of the J values owing to multiple scattering in an optically thick medium of various optical depths, various single-scattering albedos of the scattering medium, and a range of surface albedos. We have applied the results to the calculation of J values in clouds in the terrestrial atmosphere and in the Rayleigh-scattering atmosphere of Uranus. We note that J values in a realistic atmosphere may be enhanced by as much as a factor of 5 throughout a large fraction of the atmosphere over those calculated without multiple scattering and surface reflection.

scholarly journals Using passive and active microwave observations to constrain ice particle models

2019 ◽  
Author(s):  
Robin Ekelund ◽  
Patrick Eriksson ◽  
Simon Pfreundschuh
Keyword(s):  
Deep Convection ◽  
Microwave Remote Sensing ◽  
Single Scattering ◽  
The Other ◽  
Scattering Data ◽  
Particle Model ◽  
Large Set ◽  
Model Framework ◽  
Statistical Point ◽  
The One

Abstract. Satellite microwave remote sensing is an important tool for determining the distribution of atmospheric ice globally. The upcoming Ice Cloud Imager (ICI) sensor will provide unprecedented measurements at sub-millimetre frequencies, employing channels up to 664 GHz. However, the utilization of such measurements requires detailed data on how individual ice particles scatter and absorb radiation, i.e., single scattering data. Several single scattering databases are currently available, with the one by Eriksson et al. (2018) specifically tailored to ICI. This study attempts to validate and constrain the large set of particle models available in this database, to a smaller and more manageable set. A combined active and passive model framework is developed and employed, which converts CloudSat observations to simulated brightness temperatures (TBs) measured by the GPM Microwave Imager (GMI) and ICI. Simulations covering about one month in the tropic pacific ocean are performed, assuming different microphysical settings realized as combinations of particle model and particle size distribution (PSD). Firstly, it is found that when the CloudSat inversions and passive forward model are considered separately, assumed particle model and PSD have a considerable impact on both radar retrieved ice water content (IWC) and simulated TBs. Conversely, when the combined active and passive framework is employed instead, the uncertainty due to assumed particle model is significantly reduced, essentially due to a compensation effect between bulk extinction at passive frequencies and radar reflectivity. Furthermore, simulated TBs for almost all the tested microphysical combinations, from a statistical point of view, agree well with GMI measurements (186.31 and 190.31 GHz), indicating the robustness of the simulations. However, it is difficult to identify a particle model that outperforms any other. One aggregate particle model, composed of columns, yields marginally better agreement to GMI compared to the other particles, mainly for the most severe cases of deep convection. Of tested PSDs, the one by McFarquhar and Heymsfield (1997) is found to give the best overall agreement to GMI and also yields radar dBZ-IWC relationships closely matching measurements by Protat et al. (2016). Only one particle, modelled as an air-ice mixture spheroid, performs poorly overall. On the other hand, simulations at the higher ICI frequencies (328.65, 334.65, and 668.2 GHz) show significantly higher sensitivity to the assumed particle model. This study thus points to the potential use of combined ICI and 94 GHz radar measurements to constrain ice hydrometeor properties in radiative transfer (RT), using the method demonstrated in this paper.

scholarly journals IV. On the rings produced by crystals when submitted to cir­cularly polarized light

1872 ◽  
Vol 20 (130-138) ◽  
pp. 333-335
Keyword(s):  
Main Part ◽  
Wave Length ◽  
Polarized Light ◽  
Crystal Plate ◽  
The Other

The general optical arrangements here used are known. Particular cases of the phenomena resulting from it have been described by Fresnel and by Airy; and more have doubtless been observed by others. The main part of the apparatus consists, so far as polarization is concerned, of the ordinary polarizer P, analyzer A, and crystal plate to be examined, C. To this are added two quarter-undulation plates of mica, Q, Q 1 , one of which, Q, is placed below and the other, Q 1 , above the crystal C. Let i, a, b, j be the angles between the principal sections of P, Q, C, Q 1 , A, taken two and two together in the order written, all the angles being considered to be of the same sign when measured in the same direction—say, positive with that of a clock-hand. Then, if θ be the retardation produced in any ray, whose wave-length is λ, by the crystal C, the intensity of the ordinary image at any point is given (Verdet, ‘Legons d’Optique Physique,’ tome ii. p. 201*) by the formula I 2 = cos 2 (j - i) cos 2 (a + b) + sin 2 (j + i) sin 2 (a + b) + (cos 2 i sin 2 a sin 2 b cos2 j - sin 2 i sin 2 j ) sin 2 θ /2 + (cos 2 i sin 2 a sin 2 j - sin 2 i sin 2 b cos2 j sin θ /2 cos θ /2.

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