Home Science Physics Matter & Energy Alternate titles: Röntgen radiation, X-radiation Show Summary Read a brief summary of this topicX-ray, electromagnetic radiation of extremely short wavelength and high frequency, with wavelengths ranging from about 10−8 to 10−12 metre and corresponding frequencies from about 1016 to 1020 hertz (Hz). X-rays are commonly produced by accelerating (or decelerating) charged particles; examples include a beam of electrons striking a metal plate in an X-ray tube and a circulating beam of electrons in a synchrotron particle accelerator or storage ring. In addition, highly excited atoms can emit X-rays with discrete wavelengths characteristic of the energy level spacings in the atoms. The X-ray region of the electromagnetic spectrum falls far outside the range of visible wavelengths. However, the passage of X-rays through materials, including biological tissue, can be recorded with photographic films and other detectors. The analysis of X-ray images of the body is an extremely valuable medical diagnostic tool. X-rays are a form of ionizing radiation—when interacting with matter, they are energetic enough to cause neutral atoms to eject electrons. Through this ionization process the energy of the X-rays is deposited in the matter. When passing through living tissue, X-rays can cause harmful biochemical changes in genes, chromosomes, and other cell components. The biological effects of ionizing radiation, which are complex and highly dependent on the length and intensity of exposure, are still under active study (see radiation injury). X-ray radiation therapies take advantage of these effects to combat the growth of malignant tumours. X-rays were discovered in 1895 by German physicist Wilhelm Konrad Röntgen while investigating the effects of electron beams (then called cathode rays) in electrical discharges through low-pressure gases. Röntgen uncovered a startling effect—namely, that a screen coated with a fluorescent material placed outside a discharge tube would glow even when it was shielded from the direct visible and ultraviolet light of the gaseous discharge. He deduced that an invisible radiation from the tube passed through the air and caused the screen to fluoresce. Röntgen was able to show that the radiation responsible for the fluorescence originated from the point where the electron beam struck the glass wall of the discharge tube. Opaque objects placed between the tube and the screen proved to be transparent to the new form of radiation; Röntgen dramatically demonstrated this by producing a photographic image of the bones of the human hand. His discovery of so-called Röntgen rays was met with worldwide scientific and popular excitement, and, along with the discoveries of radioactivity (1896) and the electron (1897), it ushered in the study of the atomic world and the era of modern physics.  Britannica Quiz 36 Questions from Britannica’s Most Popular Science Quizzes How well do you know astronomy? How about quantum mechanics? This quiz will take you through 36 of the hardest questions from Britannica’s most popular quizzes about the sciences. Only the best quizmasters will finish it.
Author Information Author AffiliationsAndrew D. Yablon, Norman S. Nishioka, Bora B. Mikić, and Vasan Venugopalan A. D. Yablon and N. S. Nishioka are with the Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston, Massachusetts 02114. B. B. Mikić is with the Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. V. Venugopalan () is with the Laser Microbeam and Medical Program, Beckman Laser Institute, 1002 Health Sciences Road, University of California, Irvine, Irvine, California 92612. Corresponding author: Address correspondence to V. Venugopalan, Laser Microbeam and Medical Program, Beckman Laser Institute, 1002 Health Sciences Rd., University f California, Irvine, Irvine, CA 92612. Not Accessible Your library or personal account may give you access AbstractWe describe a spectroscopic technique called interferometric photothermal spectroscopy (IPTS) that can measure the absorption coefficient of pulsed laser radiation in nonscattering tissue samples. The technique is suitable for measuring effective absorption coefficients from 103 to 105 cm-1. IPTS is particularly attractive because it requires minimal disturbance of the sample. These features indicate potential use for in vivo measurements of tissue absorption coefficients. To validate the technique, the absorption coefficient of pulsed Q-switched Er:YSGG (2.79-µm) radiation in pure water was measured to be 5200 (±500) cm-1 when IPTS was used, in agreement with other published values. IPTS was also used to measure the absorption coefficient of pulsed ArF excimer laser radiation (193 nm) in bovine corneal stroma (in vitro), giving a value of 1.9 (±0.4) × 104 cm-1. © 1999 Optical Society of America Full Article | PDF Article Corrections Andrew D. Yablon, Norman S. Nishioka, Bora B. Mikić, and Vasan Venugopalan, "Measurement of tissue absorption coefficients by use of interferometric photothermal spectroscopy: erratum," Appl. Opt. 38, 4266-4266 (1999) More Like This ReferencesYou do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution. Contact your
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administrator MetricsWhat is difference between TLD and film badge?TLDs can measure a greater range of doses compared to film badges. Doses from TLDs may be easily obtained. TLDs can be read on site instead of being sent away for development. TLDs are easily reusable.
What is a thermoluminescent dosimeter used for?A small device used to measure radiation by measuring the amount of visible light emitted from a crystal in the detector when exposed to ionizing radiation.
What is TLD in radiation?Thermoluminescence dosimetry (TLD) is a versatile tool for the assessment of dose from ionising radiation. The wide variety of TLD materials and their different physical forms allow the determination of different radiation qualities at dose levels from microGy to kGy.
What are the components of TLD?TLD is a fixed-dose combination of TDF 300 mg, 3TC 300 mg, and DTG 50 mg. TLD is also recommended for use as a second-line regimen for patients failing on efavirenz- or nevirapine-containing regimens or for those failing a non-DTG-containing first-line regimen.
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