Department of Physics

Department News

Graduate Seminar Announcement for April 7

Apr 7, 2014

*****Seminar Announcement*****
PHYS 600, Monday, April 7, 4:00 pm
Currens Hall 205
All physics faculty and students are invited.

Speaker: Ashish Adhikari
Graduate Student, Physics Department, WIU
Title: Raman Spectroscopy

Abstract:

Spectroscopy is the study of objects based on the spectrum of wavelength they emit, absorb or reflect. Raman Spectroscopy is a spectroscopic technique used to observe vibrational, rotational and other low-frequency modes in a system. It is based on inelastic scattering of monochromatic light. This phenomenon was discovered by Sir C.V Raman in 1928. He was awarded by Nobel Prize in 1930 for this discovery. Raman spectra are acquired by irradiating a sample with a powerful laser source of visible or near-infrared monochromatic radiation. Photons of the laser light are absorbed by the sample and then re-emitted. The frequency of the reemitted photons is shifted up or down in comparison with the original monochromatic frequency due to the absorption of an existing phonon or the creation of a phonon within the material, which is called the Raman Effect. Phonon is a quantum mechanical description of an elementary vibrational motion in which a lattice of atoms or molecules uniformly oscillates at a single frequency. This shift provides information about vibrational, rotational and other low frequency transitions in molecules that correspond to the phonon modes in that material. Raman spectroscopy can be used to analyze a wide range of materials, including gases, liquids, and solids. This technique has application in various fields like biomedical, nanotechnology, forensic and mineralogy. Today, Raman spectroscopy is becoming more and more important. It has reached into different areas of our lives by recent developments in laser technology, more sensitive detectors, robust spectrometer optics, and last but not least, through its ease of use.

Speaker: Aysh Madkhli
Graduate Student, Physics Department, WIU
Title: Liquid Crystal Displays

Abstract:

Liquid Crystal Displays (LCD) have become less expensive and are used in nearly every electronic device, including laptops, digital clocks, microwave ovens and digital watches. LCDs are common because they offer more advantages than other display technologies, for example, LCDs are thinner and use less power compared to cathode ray tubes. There are two types of LCDs: active matrix liquid crystal display (AMLCD) and passive matrix (Twisted Nematic, TN). AMLCDs have better color production and low weight, and TNs contain liquid crystal elements which twist and untwist at varying degrees to allow light to pass through. There are other contenders in the leadership for display technology, such as organic light emitting diodes and plasma displays. LCD panels are the most suitable technology regarding energy consumption, viewing angle and response time. The only major weakness of LCD technology is the shift in color that occurs at large viewing angles.

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