Fivs 215 exam 2
Mineral Fibers (Asbestos)
(Asbestos)
Double refraction
(Calcite Romb) A dot on a paper (or ray of light) gave rise to two images when viewed through a rhomb of calcite. -different heights because different values of refractive indices O ray- ordinary ray OPE- extraordinary or E ray
Crystal Morphology(Equant, Columnar, Tabular, ConstantFace Angles)
(Equant, Columnar, Tabular, ConstantFace Angles)
Moderate Birefringence (Olefins, Nylon
(Olefins, Nylon (cellose)
High Birefringence (Polyester)
(Polyester)
Central-Stop D.S. and Annual
(Right) Annular and Central stop colors.(The two stops produce complimentary colors).To produce dispersion staining colors, the particles and immersion liquids must have different dispersion curves which intersect sharply in the visible light region
Polymers "Poly-glucose"(Cellulose, Rayon
(cellulose, rayon)
Fiber Shapes (X-Section vs Longitudinal)
(cylindrical, trilobal, dogbone or dumbell, mutliserrated
Orthoscopic vs. Conoscopic Viewing
-distortion free view parallel rays (front focal plane) vs, -Cone of converging ray of light (back focal plane)
Parallel, Oblique, Symmetrical Extinction
0 degrees- parallel45 degrees- symmetricalany other angle is oblique
Eight common optical properties of fibers
1) Brightness in some positions between crossed polars, except glass fibers which are isotropic(and, therefore, have only one value for R.I.) 2) Complete or incomplete extinctionMan-made fibers and silk show complete extinction except if they have been deformed. Cotton has incomplete extinction due to its spiral structure and twisted ribbon.Linen and many other bast fibers show cross striations between crossed polars, because of dislocation of fibrils during bending
Color temperature
2000k-8000kcandlelight to snow, water, and blue sky
Uniaxial and Biaxial Indicatrix Figures
3 central sections of uniaxial- principle section, circular section, and random section -biaxial indicatrix- triaxial ellipsoid. three axes, x,y,z
cont.
3) Extinction parallel to a prominent direction (length of fibers) 4) Order of polarization color(retardation)Learn to recognize fabric-making fibers (of low denier) by low birefringence (acrylic; cellulose acetate), moderate (nylon, cellulose),high (polyester).
cont
5) Quantitative birefringence from retardation andthickness (via a Michel-Levy chart: acrylic, 0.001 to0.004; acetate, .005 nylon, 0.07; cellulose 0.03 to 0.05;polyester, 0.10 to 0.15 -Increasing Birefringence ModacrylicAcetate Rayon Olefin Teflon Nylon PolyesterAcrylicTriacetate 6) Optical SignMost fibers are positive. Exceptions are acrylic,cellulose triacetate. 7) Refractive index for vibrationperpendicular (n┴)Cellulose acetate n ┴ = 1.475Dacron polyester n ┴ = 1.537Refractive index for vibration parallel (n II)Cellulose acetate n II= 1.47-1.48Dacron polyester n II= 1.68
Birefringence
=Retardation/1000 xt - absolute value of the diff between 'e' and "w"- independent of sample thickness - the optical property of a material having a refractive index that depends on the polarization and propagation direction of light
Monochromatic Interference Filter
? polarized monochromatic light may be extinguished by the analyzer after passing through an anisotropic mineral
Becke Line
A bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index- If ns> nm, high refractive index, halo goes inward-if ns<nm, low refractive index, halo goes outward-Halo moves toward higher medium on upward focusing
Phase Contrast Microscopy (PCM)
A contrast technique in which the phase position of the non-diffracted light is shifted in relation to the diffracted wave fronts, thereby improving the constructive and destructive interference conditions. typically used for glass chips and semen phase plate | objective | Condenser | light ring
Spindle Stage or Goniometer
A spindle stage is a rotation device with a needle/thin object on a stage that holds a crystal for rotation. -identifies crystal
Satin Weave
A weave that produces a smooth, shiny-surfaced fabric resulting from passing the weft yarn over and under numerous warp yarns to create long floats.
Distortion
Barrel Distortion- magnification decreases as you go out Pin Cushion Distortion- magnification increases as you go further out
"x"-alpha, ""-beta, and "γ "-gamma rays
Beta->Slow rays parallel- additive compensator Gamma-> Subtractive compensator
Cotton
Characteristics (Incomplete Extinction, Spiral Structure, Lumen, Undulation,Amber Retardation Color)
Optic Sign
E-W= Optic Sign -positive and negative, blue in quadrant 1 and 3 is positive, yellow in 1 and 3 is negative. -most fibers are positive except some acrylics and triacetates -
EXCALIBR
Excalibur is used to upload the points of extinction seen from rotating a crystal on a stage which can later be used for reference when identifying other materials.
Isotropic Indicatrix
For isotropic minerals the indicatrix is a sphere as can be seen here. The indicatrix can be placed anywhere within or on a crystal so long as the crystallographic directions in the indicatrix are moved parallel to themselves.
Retardation
Formula=birefringence x thickness x 1000 -Depends on birefringence and thickness as well as sample orientation -Additive-> results when the slow rays of two materials are vibrating parallel plane -Subtractive-> results when slow rays are vibrating perpendicular
What is an "interference" filter?
Has a mirrored surface that makes destructive interference, eliminating everything except the wavelength of interest.
Isotropism & Anisotropism
Isotropism-light vibrates in the same way when an object is moved around in diff directions. no light visible Anisotropism-different properties shown when moving an object. light seen as object is moved
Bast Fibers-
Jute, Ramie, Sisal, HempMarijuana ID by Leaf Fibers (Cystolith Hairs, Conical Trichomes, Glandular Hairs)
("Hoffman") Modulation Contrast
Modulator | Objective | condenser | slit A Slit allows light to come in at oblique angle so one side of image is bright and the other is dark.
Synthetic Fibers
Nylons, polyesters, polyolefins, polyethylenes and polyproyplenes, acrylics, saran, vinyon, elastic, glass, metallic
What crystal lattice structure(s) exhibit biaxial interference figures?
Orthorhombic, Monoclinic, and Triclinic crystal lattice structures exhibit biaxial interference.
Oblique Illumination
Particle appears to be shaded on the same side as the shaded field view= index of particle is higher-Particle appears to be shaded on the opposite side of the shaded field view= index of particle is lower Higher contrast due to angle of light
Synthetic fibers
Poly-esters, Poly-amides (Nylons),Poly-olefins (Polyethylenes &Polypropylenes)
Regenerated Fibers (Rayon, Acetates)
Rayon, Acetates
What crystal lattice structure(s) exhibit uniaxial interference figures?
Tetragonal, Hexagonal, and Rhombohedral.
Dispersion Staining (D.S.)
The contrast technique that utilized a central stop and an annual stop to produce "colors", which can be used to help identify the sample
Plain Weave
The simplest weave in which the weft (crosswise) yarn is passed over then under each warp (lengthwise) yarn.
What do you call the type of polarizing light microscopy viewing, which utilized an Amici-Bertrand lens, and observed the back focal plane of the objective?
This type of Polarizing light microscopy is called Conoscopic interference.
Optic Angle (2V, 2H, 2E)
Tobi's method-relationship between angular aperture; axial angles 2E, 2H, and 2V; and linear diameters of back focal plane of objective.
Uniaxial and Biaxial Interference Figures
Uniaxial- cross with yellow and blue quadrants, cross doesn't disappear when moved. Positive if E >O-> Blue in quadrants 1 and 3=additive Negative if E<O-> Yellow is in 1&3 -Biaxial- hyperbolas in quadrants 2 and 4 which will rotate as the stage is rotated. (Ortho,Mono,and TRi)
How do you determine whether an interference figure is uniaxial or biaxial?
When observing Uniaxial interference, the specimen will create a "cross" with four quadrants which typically stay in the same structure when the stage is moved. Biaxial interference creates hyperbolas in quadrants 2 and 4 which will rotate as the stage is rotated.
Animal Fibers (Wool, Silk, DomesticDog/Cat, Fur Animals)
Wool-(Important textile) Silk- (From Silkworm Bombyx mori) Other Animal Fibers (Furs, Domesticated
Pleochroism
a material which exhibits a change in intensity or hue when its orientation to plane polarized light changes (rotation of the stage) A substance that has different colors when observed at different angles, with polarized light, it changes its hues when you rotate the stage.
Twill Weave
a textile weave in which threads are crossed over one another to give an appearance of diagonal lines.
Modified Herzog Test
an empirical test for determining the fibrillar orientation using polarized light microscopy.
Spherical
areas or zones of the lens that are closer to its periphery are stronger (shorter focal lengths) than zones near axis of lens. (fuzzy image)
Cross-Striations (Bast Fibers-Dislocated Fibrils)
bast fibers- dislocated fibrils, shown between crosses polars, because of dislocation oof fibrils during bending.
Monomers (Glucose)
building blocks of polymers glucose
"w" or "o" ray, "E" or "e" ray
calcite rhomb rays, ordinary ray (predictable path) and extraordinary ray (obvious contradiction of snell's law). - O and E ray vibrate perpendicular to each other
Curvature of field
can focus the image in one particular plane
Warp and Weft or Fill
components used in weaving to turn thread into fabric.
Complete Extinction (Synthetic Fibers)
man-made fibers and silk show complete extinction unless they have been deformed.
Immersion Methods for RI Measurement
match point detection: Becke line, obliqueRI variation: liquids, temp and wavelength variation Temp and wavenlength affect Refractive Index
Differential Interference Contrast (DIC)
microscope that uses a prism to split the incident beam into two mutually perpendicular components. analyzer makes the vibration directions parallel so light rays can interfere at the intermediate image plane.
Low Birefringence (Acrylics, Acetates)
modacrylic, acetate, acrylic, triacetate
Optic Sign (Most fibers are positiveexcept some Acrylics, and Triacetates)
most fibers are positive except some acrylics and triacetates
Bright Field Microscopy
produces an image made from light that is transmitted through a specimenspecimen against a light background
Astigmatism
rays traveling through two perpendicular planes of the lens are focused at different distances. -("1" & "2"). At "1" only the vertical diameter of object "O" is in focus, while horizontal diameter is not yet in focus, causing this diameter to be fuzzy and elliptical. At"2" the opposite occurs. (horizontal diameter will be fuzzy and elliptical)
Delustering Agents
reduces the sheen of synthetic fibers.
Vegetable Fibers(Seed Hairs-Cotton, Kapok)
seed hairs - cotton, kapok -Bast or Stem Fiber- (ie; Linen, Manila, Hemp) -Trichomes or Leaf hairs- (ie; Cannabis sativa) unicellular and used as individual fibers rather than bundles.wool, silk, fur or domesticated
Dark Field Microscopy
shows the specimen against a dark background and provides good resolution
Silk- Bombyx Mori (Looks Synthetic)
silk from a moth
Aberrations
spherical, chromatic, curvature of field, distortion, astigmatism
GRIM
there an instrument that can make refractive index measurements "automatically Glass refractive index -> uses light and temp to graphically plot refractive index of glass Used instead of the oil
Chromatic
transparent materials do not refract all wavelengths equally Longitudinal- diff focal point Lateral- diff magnification
Wayne Williams Case
tried for the murder of two individuals in the Atlanta, Georgia An essential part of the government's case was the numerous fibers linking Williams to the murders yellow-green fibers discovered on a number of the murder victims were linked to a carpet in the Williams home which helped proved his guilt
Calcite Rhomb (Icelandic Spar)
two dots, one moves around the other and they appear to be on different levels. When using polaroid, one dot disappears. When two are moved together, film turns entirely dark when positioned in a certain way different heights because different values of refractive indices
Fabric construction
weaves (warp and weft and will), knits (human and machine-made), felts (non-woven fabrics), nets, lace, and braided
Sign of Elongation
when crystal length is also the high index direction, sign of elongation is positive. low index = negativeoften applied to fibers -Pos optic sign
