|
Polarizing Microscope
A petrographic microscope is a type of optical microscope used in petrology and optical mineralogy to identify Rock (geology), rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks. The method is called "polarized light microscopy" (PLM). __TOC__ Description Depending on the grade of observation required, petrological microscopes are derived from conventional Bright-field microscopy, brightfield microscopes of similar basic capabilities by: * Adding a Nicol prism polarizer filter to the light path beneath the sample slide * Replacing the normal stage with a circular rotating stage (typically graduated with vernier scales for reading orientations to better than 1 degree of arc) * Adding a second rotatable and removable Nicol prism filter, called the analyzer, to the light path between objective and eyepiece * Adding a phase telescope, also known as a Bertran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vernier Scale
A vernier scale, named after Pierre Vernier, is a visual aid to take an accurate measurement reading between two graduation markings on a linear scale by using mechanical interpolation, thereby increasing resolution and reducing measurement uncertainty by using vernier acuity to reduce human estimation error. It may be found on many types of instrument measuring linear or angular quantities, but in particular on a vernier caliper which measures internal or external diameter of hollow cylinders. The vernier is a subsidiary scale replacing a single measured-value pointer, and has for instance ten divisions equal in distance to nine divisions on the main scale. The interpolated reading is obtained by observing which of the vernier scale graduations is coincident with a graduation on the main scale, which is easier to perceive than visual estimation between two points. Such an arrangement can go to a higher resolution by using a higher scale ratio, known as the vernier constant. A v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harry Rosenbusch
(Karl) Heinrich/Harry (Ferdinand) Rosenbusch (24 June 1836 – 20 January 1914) was a German petrographer. Harry Rosenbusch was born in Einbeck. He taught at Heidelberg University (1877–1908), where he founded the ''Mineralogisches-geologisches Institut''. He died, aged 77, in Heidelberg Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of students .... Literary works * ''Mikroskopische Physiographie der petrographisch wichtigen Mineralien'', 1873 * ''Mikroskopische Physiographie der Mineralien und Gesteine'', 4 Vols., 1873-1877 * ''Elemente der Gesteinslehre'', 1898 * ''Mikroskopische Physiographie'' (4th ed., Stuttgart, 1909, 2 vols.) References External links * — He is mention a number of times in the article specifically: "the more basic minerals precede the less basic; ... is known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giovanni Battista Amici
Giovanni Battista Amici (; 25 March 1786 – 10 April 1863) was an Italian astronomer, microscopist, and botanist. Amici was born in Modena, in present-day Italy. After studying at Bologna, he became professor of mathematics at Modena, and in 1831 was appointed inspector-general of studies in the Duchy of Modena. A few years later he was chosen director of the observatory at Florence, where he also lectured at the museum of natural history. Amici died in Florence in 1863. His name is best known for the improvements he effected in the mirrors of reflecting telescopes and especially in the construction of the microscope. He was also a diligent and skillful observer, and busied himself not only with astronomical subjects, such as the double stars, the satellites of Jupiter and the measurement of the polar and equatorial diameters of the sun, but also with biological studies of the circulation of the sap in plants, the fructification of plants, infusoria etc. He was the first to obs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarizer
A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well-defined polarization, that is polarized light. The common types of polarizers are linear polarizers and circular polarizers. Polarizers are used in many optical techniques and instruments, and polarizing filters find applications in photography and LCD technology. Polarizers can also be made for other types of electromagnetic waves besides visible light, such as radio waves, microwaves, and X-rays. Linear polarizers ''Linear polarizers'' can be divided into two general categories: absorptive polarizers, where the unwanted polarization states are absorbed by the device, and beam-splitting polarizers, where the unpolarized beam is split into two beams with opposite polarization states. Polarizers which maintain the same axes of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Nicol (geologist)
William Nicol FRSE FCS (1768?2 September 1851) was a Scottish geologist and physicist who invented the Nicol prism, the first device for obtaining plane-polarized light, in 1828. Early life Nicol was born in Humbie (East Lothian), the son of Walter Nicol and Marion Fowler. According to the parish register, he was baptised on 18 April 1770. Some sources give his date of birth as 1768; other ones (including his gravestone) give 1766. (Note that the gravestone date may be incorrect, as the engraving was done at least 50 years after his death.) Lecturer He started out as aide to his uncle, Henry Moyes, an itinerant lecturer in Natural Philosophy whose blindness necessitated assistance for his chemistry and optics demonstrations.''Joseph Priestley to Joseph Banks'', 6 Feb 1783, NHM, Dawson Turner MS 3, fol. 17p122 Albert Edward Musson, Eric Robinson ''Science and technology in the Industrial Revolution,'' Manchester University Press, 1969, Nicol, having himself become a popular l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Étienne-Louis Malus
Étienne-Louis Malus (; ; 23 July 1775 – 23 February 1812) was a French officer, engineer, physicist, and mathematician. Malus was born in Paris, France. He participated in Napoleon's expedition into Egypt (1798 to 1801) and was a member of the mathematics section of the Institut d'Égypte. Malus became a member of the Académie des Sciences in 1810. In 1810 the Royal Society of London awarded him the Rumford Medal. His mathematical work was almost entirely concerned with the study of light. He studied geometric systems called ''ray systems'', closely connected to Julius Plücker's ''line geometry''. He conducted experiments to verify Christiaan Huygens's theories of light and rewrote the theory in analytical form. His discovery of the polarization of light by reflection was published in 1809 and his theory of double refraction of light in crystals, in 1810. Malus attempted to identify the relationship between the polarising angle of reflection that he had discovered, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffraction
Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word ''diffraction'' and was the first to record accurate observations of the phenomenon in 1660. In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringence
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conoscopy
Conoscopy is an optical technique to make observations of a transparent specimen in a cone of converging rays of light. The various directions of light propagation are observable simultaneously. A conoscope is an apparatus to carry out ''conoscopic observations'' and measurements, often realized by a microscope with a Bertrand lens for observation of the ''direction's image''. The earliest reference to the use of ''conoscopy'' (i.e., observation in convergent light with a polarization microscope with a Bertrand lens) for evaluation of the optical properties of liquid crystalline phases (i.e., orientation of the optical axes) is in 1911 when it was used by Charles-Victor Mauguin to investigate the alignment of nematic and chiral-nematic phases.Mauguin, C.: Sur les cristaux liquides de LehmannBull. Soc. Fr. Miner. 34, 71–117 (1911)/ref> A beam of convergent (or divergent) light is known to be a linear superposition of many plane waves over a cone of solid angles. The raytracing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotropy
Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence ''anisotropy''. ''Anisotropy'' is also used to describe situations where properties vary systematically, dependent on direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. Mathematics Within mathematics, ''isotropy'' has a few different meanings: ; Isotropic manifolds: A manifold is isotropic if the geometry on the manifold is the same regardless of direction. A similar concept is homogeneity. ; Isotropic quadratic form: A quadratic form ''q'' is said to be isotropic if there is a non-zero vector ''v'' such that ; such a ''v'' is an isotropic vector or null vector. In complex geometry, a line through the origin in the direction of an isotropic vecto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Plate
A waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. Two common types of waveplates are the ''half-wave plate'', which shifts the polarization direction of linearly polarized light, and the ''quarter-wave plate'', which converts linearly polarized light into circularly polarized light and vice versa. A quarter-wave plate can be used to produce elliptical polarization as well. Waveplates are constructed out of a birefringent material (such as quartz or mica, or even plastic), for which the index of refraction is different for light linearly polarized along one or the other of two certain perpendicular crystal axes. The behavior of a waveplate (that is, whether it is a half-wave plate, a quarter-wave plate, etc.) depends on the thickness of the crystal, the wavelength of light, and the variation of the index of refraction. By appropriate choice of the relationship between these parameters, it is possible to introduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
