l25 - Ionizing radiation Radiation: ionizing, and not...

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Ionizing radiation Quantifying radiation Early X-ray experience Hiroshima and Nagasaki Bystander effect Low-level risks Nuclear accidents Nuclear power wrapup Radiation: ionizing, and not ra · di · a · tion noun 1 Physics the emission of energy as electromagnetic waves or as moving subatomic particles, esp. high-energy particles that cause ionization. · the energy transmitted in this way, as heat, light, electricity, etc. What’s the big deal about ionizing? Don’t we get radiation from microwave ovens, cell phone towers, and power lines?
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Ionizing radiation Quantifying radiation Early X-ray experience Hiroshima and Nagasaki Bystander effect Low-level risks Nuclear accidents Nuclear power wrapup Ionizing energies Ionization means we break chemical bonds. H-C bond: 3.5 eV per molecule. K band microwaves (police radar guns): f 20 GHz or E = hf = ( 4 . 14 × 10 - 14 eV · sec ) · ( 20 × 10 9 sec - 1 ) = 0 . 000 083 eV per photon. 60 Hz power line: E = hf = 2 . 5 × 10 - 13 eV or 0.000000 000 000 25 eV. So don’t worry about radiation from power lines, microwave ovens, or cell phone towers! National Academy study: “Based on a comprehensive evaluation of published studies relating to the effects of power-frequency electric and magnetic fields on cells, tissues, and organisms (including humans), the conclusion of the committee is that the current body of evidence does not show that exposure to these fields presents a human-health hazard. Specifically, no conclusive and consistent evidence shows that exposures to residential electric and magnetic fields produce cancer, adverse neurobehavioral effects, or reproductive and developmental effects.” http://books.nap.edu/catalog.php?record_id=5155
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Ionizing radiation Quantifying radiation Early X-ray experience Hiroshima and Nagasaki Bystander effect Low-level risks Nuclear accidents Nuclear power wrapup Quantifying radiation We’re only talking about photon and particle energies above 5–10 eV! What’s easy to calculate? Energy absorbed per mass. The SI unit is the Gray (named after a British radiation biologist): 1 Gray=1 Joule/kg. Older unit: 1 rad=1 erg/g. 1 Gray=100 rad. Different radiations α , β , γ and neutrons have slightly different Relative Biological Effectiveness or RBE. RBE factors range from around 1 to around 10 for the most part. 1 Sievert=(1 Gray) · RBE, and 1 REM=(1 Rad) · RBE. REM=Röntgen Equivalent Man. I will try to use milliSieverts or mSv throughout these slides. To get some numbers out there: 5000 mSv kills half of those exposed (LD 50 ). Natural background: 3 mSv/year. Quantities matter!
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Ionizing radiation Quantifying radiation Early X-ray experience Hiroshima and Nagasaki Bystander effect Low-level risks Nuclear accidents Nuclear power wrapup Radiation in the Garden of Eden Radiation has been part of the planet since before life began.
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This note was uploaded on 05/28/2011 for the course PHY 251 taught by Professor Rijssenbeek during the Fall '01 term at SUNY Stony Brook.

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l25 - Ionizing radiation Radiation: ionizing, and not...

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