radiation dosimetry-principle,construction?
488947
Dosimetry is the measurement of doses in matter and tissue from ionizing radiation (radioactivity, alfa decay, gamma decay, beta decay).\n\nDoses are measured in grays (Gy) for matter or sieverts (Sv) for biological tissue. \n\nThe dose refers to the amount of energy or damage deposited in the matter, and should not be confused with the unit of radioactive activity (becquerel, Bq). \n\nDoses can be measured in places other than where the radioactive decay occurred.
915684
Very roughly:  by comparing the ratio between a radioisotope and its "daughter product", and with the knowledge of the radioisotope's half-life, calculate the amount of time needed for the observed ratio to develop.\n\nIn short, if there is a 50-50 split between the radioisotope and its daughter product, one half-life has passed.
961817
Above answer is quite to the point.. i would just like to add that, if u consider a light ray entering a open window there is very less chance that it will escape out again. in short it can be assumed to be absorbed.  \n\nIn the black body radiation, we need a perfect radiator n perfect absorber.
624444
Is there a way to quantify/measure a value for solar radiation with respect to time, it seems to me like you could come up with a calculation based on the angle of the rays. However, I think you would run into some problems with exact calculations due to the nature of our atmosphere (i.e. moisture, dust, etc.)
120284
Skin reddening (erythema) can occur after exposure to radiation HOWEVER the dose of radiation introduced to a patient and a patient's skin in general diagnostic radiography is not even close to damaging enough to cause any kind of radiation burns, spots, marks, etc. The modern (ie, since we've known radiation should be handled with care) cases of radiation burns that I've seen involved intense surgical procedures where the patient was exposed to over an hour (versus 1 or 2 seconds max for regular x-rays) of high energy fluoroscopy during procedures such as cardiac cath.\n\nI'm assuming you had a chest x-ray (?). Hopefully this will make you feel better: the general rule of thumb is that a chest x-ray results in a radiation dose similar to that of what you would recieve flying in a high altitude (say, transatlatic flight) plane for several hours. Remember, as a human on earth you are constantly being exposed to radiation in the form of solar and terrestrial radiation. And, while it does need to be administered safely, that is the reason why we have "radiologic technologists" working at our hospitals. These people go through a lot of training to ensure that patients are not being over exposed.\n\nAs for why the tech had to repeat, often times a patient's individual anatomy does not allow for everything that the doctor needs to see to fit on one picture. If something is missing the tech might have to center differently and take another exposure. \n\nIt may make you feel better to know that Neonatal intensive care babies often recieve several x-rays, everyday, for weeks while they are in the hospital. As babies they are considered to be extremely sensitive to radiation and even so, with all the x-rays, they still grow up fine, healthy, and with no ill effects.\n\nI do not think you have to worry about the exposure that you recieved ;-)
171995
3K background radiation measurement instruction:\n\n\n(1) take a full spectrum snapshot of the sky sphere.\n\n(2) substract all known active radiation sources (stars)\n\n\n(3) take the resulting frequency spectrum I(n) and\n\n(3.1) assume that you know allmost each existing active radiation source\n\n(3.2) assume that the universe doesn't radiate outwards and nothing radiates into it\n\n(3.3) then you can speak of a radiation field equilibrium and are allowed to apply 'blackbody radiation' theory\n\nhttp://en.wikipedia.org/wiki/Black_body\n\n\n(4) apply 'blackbody radiation' theory to the frequency spectrum: I(n) of step (3)\n\n(4.1) fit Planck's function of blackbody radiation: I(T,n) by variation of the remaining variable T\n\n\n(5) if you get a proper fit, call the temperature T, the temperature of the universe.\n\n\nuntil now, all such measurements led to T = 3 Kelvin.\nBut this doesn't mean that empty space would have a temperature itself.
421381
Several Units actually and they can be a bit confusing\n\nRad, Rem, Seiverts, grey, etc etc\n\n\nhere is the break down\n\nKerma = Kinetic Energy transferred to charged particles in Rads / Grays.\nRad = radiation absorbed dose\n= 100 ergs of energy / gm of tissue\n= 0.01 joule of energy / kg of tissue\n1 Gray = 100 Rads = 1 joule of energy / kg of tissue\n1 Rad = 0.01 Gray\n1cGy (centi Gray) = 1 Rad\n1 mGy (milli Gray ) = 0.1 Rad\nRem = radiation equivalent man\n= rad x RBE (QF) / (relative biological effectiveness or Quality factor)\nSeivert = Gray x QF\n1 Seivert = 100 rems \n(1000 milliSv or mSv)\n1 mSv = 0.1 rem ( for Xrays which have a qualifying factor of 1) = 1 mGy\n\n\n\nconfusing huh?  took 2 college terms on it myself
848476
Measuring the background radiation.\nCalculations involving half life.\nCalculating the energy of fusion and fission reactions.
177736
Here is what I have found:\nGamma Rays - 124 pm (pico-meter) and up\nX Rays - 10 to .1 nanometers
243458
There is a huge difference between ionizing and non-ionizing radiation.  RF radiation is non-ionizing and unless you have such high levels that you could be burned by it, there is no inherent danger - just keep below the ANSI levels.  There have been tons of epidemiological tests which show that there is no causality to cancer.  Remember that light is another source of non-ionizing radiation and people don't seem too concerned about being 'bombarded' by it.
781911
None.\n\nCalories are a measure of the heat content of objects.  If you are referring to the amount of heat radiated by the earth, it would be stated in some unit appropriate to the measure of radiant energy, such as watts or newtons per second.\n\nYou may be able to find an answer by visiting the library or using the internet.
161041
Radiation in physics is a process of emission of energy or particles. Various forms of radiation may be distinguished, depending on the type of the emitted energy/matter, the type of the emission source, properties and purposes of the emission, etc.
723674
It's sometimes used as part of radiotherapy for cancer patients, as well as possessing a variety of other uses.\n\nI'd suggest the greatest site ever - Wikipedia as the place to look.\n\nI've sourced it for your convenience.
1058287
First, this is a topic that is of continual annoyance for people who work with radiation.  Let's tackle this in sections...\n\nFirst let's start with the Roentgen.  The Roentgen (R) is defined as charge per unit mass.  Historically, it was defined as the amount of gamma or x-rays that produced one electrostatic unit of charge in 1 mL of air at STP (1.293E-3 g).  More currently, R=2.58E-4 C/Kg (C=Coulombs).\n\nOk, back to it.  A RAD is defined as 100 erg/g.  This is basically the same thing as R; a unit of charge per unit mass.  This is the "old" system unit.  This was supplanted by the SI unit of the Gray (Gy).  A Gy is defined as 1 J/kg (seeing the trend?).  Both units are a measure of Absorbed Dose (D).  Ok, if you would like to move between them, the conversion is 1 Gy = 100 RAD.  Why?\n\nOk, 1 J/Kg = 10^7 erg/10^3 g = 10^4 erg/g = 100 RAD\n\nNow, onto the Dose Equivalents.  A dose equivalent, H, is the effective dose received from ionizing radiation.  However, not all radiations are created equal.  A 1 RAD exposure to x-rays is far less harmful that a 1 RAD exposure to >10 keV neutrons.  So, a sliding scale was introduced.  For a given exposure to radiation, \n\nH=QF * D\n\nwhere QF is the quality factor and D is the absorbed dose.  Ok, back to your question.  A REM is the Dose Equivalent corresponding to Absorbed Dose in RAD.  Confused?  Ok, take a dose in RAD, multiply by the quality factor, and you get an answer in REM.  For the SI system, take a dose in Gy, multiply by the QF, and your answer is in Sieverts (Sv).  Generalized quality factors are:\n\nX and GammaRays - 1\nElectrons and Positrons - 1\nNeutrons E < 10 keV - 3\nNeutrons E > 10 keV - 10\nProtons  - 1 to 10\nAlphas - 1 to 20\nHeavy Ions - 20\n\nFor reference to the annoyance caused by the dual systems, as a radiological worker, my DOE imposed dose limit is 5 REM.  This dose is very easy to remember and seems intuitive.  However, under the SI system, my dose limit is 50 mSv, which seems small, though they represent the same physical quantity.
559938
If u are a student , then u should not be lazy in doing your homework etc.  \n\n\nCriticality accidents:\n\nCriticality accidents and power excursions in nuclear reactors, for example the Chernobyl accident. In a smaller scale accident at Sarov a technician working with highly enriched uranium was irradiated while preparing an experiment involving a sphere of fissile material. The Sarov accident is interesting because the system remained critical for many days before it could be stopped, though it was safely located in a shielded experimental hall. This is an example of a limited scope accident where only a few people can be harmed, while no release of radioactivity into the environment occurred. A criticality accident with limited off site release of both radiation (gamma and neutron) and a very small release of radioactivity occurred at Tokaimura in 1999 during the production of enriched uranium fuel .\n\n\nDecay heat:\n\nDecay heat accidents where the heat generated by the radioactive decay causes harm. In a nuclear reactor that has been shut down, a loss of coolant accident can damage the core, for instance at Three Mile Island a recently shutdown PWR reactor was left for a length of time without cooling water. As a result the nuclear fuel was damaged, and the core was partly melted.\n\nTransport:\n\nTransport accidents can cause a release of radioactivity resulting in contamination or shielding to be damaged resulting in direct irradiation. In Cochabamba a defective gamma radiography set was transported in a passenger bus as cargo. The gamma source was outside the shielding, and it irradiated some bus passengers.\n\nIn the United Kingdom, it was revealed in a recent court case that a radiotherapy source was transported from Leeds to Sellafield with defective shielding. The shielding had a gap on the underside. It is thought that no human has been seriously harmed by the escaping radiation.\n\n\nEquipment failure:\n\nEquipment failure is one possible type of accident, recently at Białystok in Poland the electronics associated with a particle accelerator used for the treatment of cancer suffered a malfunction . This then lead to the overexposure of at least one patient. While the initial failure was the simple failure of a semiconductor diode, it set in motion a series of events which led to a radiation injury.\n\n\nHuman error:\n\nHuman error has been responsible for some accidents, for instance a person miscalculated the activity of a teletherapy source. This then lead to patients being given the wrong dose of gamma rays. In the case of radiotherapy accidents, an underexposure is as much an accident as an overexposure as the patients may not get the full benefit of the proscribed treatment. Also, humans have made errors while attempting to service plant and equipment which has resulting in overdoses of radiation, such as the Nevvizh and Soreq irradiator accidents.\n\n\nLost source:\n\nLost source accidents are ones in which a radioactive source is lost, stolen or abandoned. The source then might cause harm to humans or the environment. For example, see the event in Lilo where sources were left behind by the Soviet army. Another case occurred at Yanango where a radiography source was lost, also at Samut Prakarn a cobalt-60 teletherapy source was lost  and at Gilan in Iran a radiography source harmed a welder. The best known example of this type of event is the Goiânia accident which occurred in Brazil.\n\nThe IAEA have provided guides for scrap metal collectors on what a sealed source might look like. The scrap metal industry is the one where lost sources are most likely to be found.\n\n\nOthers:\n\nSome accidents defy classification. These accidents happen when the unexpected occurs with a radioactive source. For instance if a bird grabs a radioactive source containing radium from a windowsill and then was to fly away with it, returning to its nest and then the bird dies shortly afterwards from direct irradiation then i
569245
Everything in this universe emanates radiation, including your body. The only exception is objects that are already at absolute zero.
1023911
Electromagneticradiation