SUMMARY / RELATED TOPICS

Polarimetry

Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object.plane polarized light: according to the wave theory of light an ordinary ray of light is consider to be vibrating in all planes of right angles to the direction of its propagation if this ordinary ray of light is passed through a nicol prism the emergent ray has its vibration only in one plane. Polarimetry of thin films and surfaces is known as ellipsometry. Polarimetry is used in remote sensing applications, such as planetary science and weather radar. Polarimetry can be included in computational analysis of waves. For example, radars consider wave polarization in post-processing to improve the characterization of the targets. In this case, polarimetry can be used to estimate the fine texture of a material, help resolve the orientation of small structures in the target, when circularly-polarized antennas are used, resolve the number of bounces of the received signal.

In 2003, a visible-near IR Spectropolarimetric Imager with an acousto-optic tunable filter was reported. These hyperspectral and spectropolarimetric imager functioned in radiation regions spanning from ultraviolet to long-wave infrared. In AOTFs a piezoelectric transducer converts a radio frequency signal into an ultrasonic wave; this wave travels through a crystal attached to the transducer and upon entering an acoustic absorber is diffracted. The wavelength of the resulting light beams can be modified by altering the initial RF signal. VNIR and LWIR hyperspectral imaging perform better as hyperspectral imagers; this technology was developed at the U. S. Army Research Laboratory; the researchers reported visible near infrared system data which required an RF signal below 1 W power. The reported experimental data indicates that polarimetric signatures are unique to manmade items and are not found in natural objects; the researchers state that a dual system, collecting both hyperspectral and spectropolarimetric information, is an advantage in image production for target tracking.

A polarimeter is the basic scientific instrument used to make these measurements, although this term is used to describe a polarimetry process performed by a computer, such as is done in polarimetric synthetic aperture radar. Polarimetry can be used to measure various optical properties of a material, including linear birefringence, circular birefringence, linear dichroism, circular dichroism and scattering. To measure these various properties, there have been many designs of polarimeters, some archaic and some in current use; the most sensitive are based on interferometers, while more conventional polarimeters are based on arrangements of polarising filters, wave plates or other devices. Polarimetry is used in many areas of astronomy to study physical characteristics of sources including active galactic nuclei and blazars, exoplanets and dust in the interstellar medium, gamma-ray bursts, stellar rotation, stellar magnetic fields, debris disks, reflection in binary stars and the cosmic microwave background radiation.

Astronomical polarimetry observations are carried out either as imaging polarimetry, where polarization is measured as a function of position in imaging data, or spectropolarimetry, where polarization is measured as a function of wavelength of light, or broad-band aperture polarimetry. Optically active samples, such as solutions of chiral molecules exhibit circular birefringence. Circular birefringence causes rotation of the polarization of plane polarized light as it passes through the sample. In ordinary light, the vibrations occur in all planes perpendicular to the direction of propagation; when light passes through a Nicol prism its vibrations in all directions except the direction of axis of the prism are cut off. The light emerging from the prism is said to be plane polarised because its vibration is in one direction. If two Nicol prisms are placed with their polarization planes parallel to each other the light rays emerging out of the first prism will enter the second prism; as a result, no loss of light is observed.

However, if the second prism is rotated by an angle of 90°, the light emerging from the first prism is stopped by the second prism and no light emerges. The first prism is called the polarizer and the second prism is called the analyser. A simple polarimeter to measure this rotation consists of a long tube with flat glass ends, into which the sample is placed. At each end of the tube is other polarizer. Light is shone through the tube, the prism at the other end, attached to an eye-piece, is rotated to arrive at the region of complete brightness or that of half-dark, half-bright or that of complete darkness; the angle of rotation is read from a scale. The same phenomenon is observed after an angle of 180°; the specific rotation of the sample may be calculated. Temperature can affect the rotation of light. Λ T = 100 α / l ρ where: λT is the specific rotation. T is the temperature. Λ is the wavelength of light. Α is the angle of rotation. L is the length of the polarimeter tube. Ρ is the mass concentra

Eileen Dailly

Eileen Elizabeth Dailly was an educator and political figure in British Columbia, Canada. She represented Burnaby North in the Legislative Assembly of British Columbia from 1966 to 1986 as a New Democratic Party member, she was born Eileen Elizabeth Gilmore, the daughter of Joseph Gilmore and Mary Scott, in Vancouver, British Columbia and taught school for ten years in British Columbia. In 1951, she married James Dailly, she served ten years as a school trustee and was chairman of the Burnaby School Board for four years. In the assembly, Dailly served as Minister of Education; as education minister, she banned corporal punishment in schools in 1973. She retired from politics in 1986. From 1988 to 1991, she hosted a senior's program on community cable television called "Coming of Age". Dailly died on Salt Spring Island at the age of 84 from complications following skin cancer surgery

Pontiothauma minus

Pontiothauma minus is a species of sea snail, a marine gastropod mollusk in the family Raphitomidae. The length of the shell attains 30 mm, its diameter 14 mm; the white, ovate-fusiform shell contains about eight whorls. The remaining whorls are somewhat convex below, they contains angulate whorls. These are about eighteen in number, somewhat acute, do not reach to the suture above, but terminate at the depression at the upper part of the whorls; the transverse lirae are fine and continuous over and between the ribs. The white aperture measures about half the length of the shell; the thin outer lip is sinuate at its top. The columella contains a white callus; the siphonal canal is wide and somewhat recurved. The animal is without eyes or operculum, the foot is much flattened behind; this marine species occurs off Sri Lanka. Tucker, J. K.. "Catalog of recent and fossil turrids". Zootaxa. 682: 1–1295. Doi:10.11646/zootaxa.682.1.1