Tritium has a half-life of 12.3 years. How many years will elapse when the radioactivivty of tritium sample diminishes to 10% of its original value?
217345
Here is another way\n\nHalflife           Quantity Left\n1                       1/2\n2                        1/4\n3                        1/8 (.125)\n4                          1/16 (.0625)\n\nYou can see that it will be between 3 and 4 halflives\nor between 36.9 and 49.2 years ( about 40 years approx.)
264671
Ok I think that what you don't understand and what really has not been pointed out yet is that radiation is produced by the decay ( or breakdown) of atoms in the nuclear material.\n\nSay you have a few pounds of nuclear waste. You have Billions and billions and billions of atoms. Remember Avogadro's number? That is the number in just a mole of material. Now imaging that number multiplied by the number of moles in a few pounds! That's a lot of atoms.\n\nNow a fire burns out because it runs out of material to burn. However with all those billions of atoms it could take tens of thousands of years for all the material to be used up.\n\nie if the half life is 10,000 years, that means we have only used up half the material in 10,000 years. So if we had 10 pounds of nuclear waster, in 10,000 years we would still be left with 5 pounds!\n\nNow think of Einsteins famous equation E=mc2.\nm is the mass, c is the speed of light squared, and E is the\nenergy you get out of it. As you can see, even in a very small amount of mass there is tremendous energy.\n\nSo sum it up, even though very small amounts are decaying and giving off large amounts of energy. It is going to take thousand and thousands of years before it is used up.that is why it lasts so long.
101675
The half time for decay of C14 is about the same as the biblically calculated age of the earth by change.\nThe decay time is constant and the age grows.\nThe margin is a couple of years, depending on the measured time. The longer you count the more precise the result.
208566
Francium is radioactive. Its most stable isotope has a half life of only 20 minutes or so. \nThis means that the only Francium present in the earth crust are those atoms that originated from other atoms having decayed. Francium has been detected in Uranium ores but the total quantity present at any time does not exceed 20 grams or so.
558574
That's a loaded question.  Depending on the type of energy you wish to know about estimates are anywhere from 15,000 years to about 48 million years, though most agree that an average of between 40,000 to 1,000,000 years is the most likely result.  Whats the leason here? Randomization and re-emitance can wreak havoc if your some guy trying to make good travel time.
13774
first of all, it isn't necessarily 100,000 years.  the radioactive waste is made up of radioactive elements.  the only way to measure the wasting of the radioactivity of a material is by half-life, or the time it takes for half of the waste to lose its radioactivity.  essencially, the waste will always be active, but eventually the amount that it is giving off decreases to an amount that doesn't affect humans.  weather it's 100,000 or 1000000 years depends on the material and how much of it.\n\nthe waste will always be there, but nuclear waste is really just radioactive atoms of elements like plutonium, uranium, etc.  it won't disappear, but it will eventually become harmless.
221758
The question is a little bit muddled, but I think I get the idea.\n\nThe atoms that are exposing the age of things are those atoms that are, or were, radioactive.  Any radioactive material decays.  It also decays at predictable, measurable rates that are distinctive to the element.  So you can date things that have radioactive elements (which most things do in some trace amount) or their decay elements within, based on how decayed they are.\n\nUranium-238 ultimately decays into lead.  You can date how long something containing uranium-238 has been in existence based on the ratio of Ur-238 to Pb.\n\nThis process operates at the same rate no matter what the temperature is.
534626
typical pH electrode life is expected to be one year from the date of manufacture for most warranty purposes. They do depend on application and application variances (i.e. how stable the solution being tested is.. amount of variance, temperature , etc). these factors all shorten electrode expected life. As far as having 10 year working electrodes.. i have heard of this, but I wouldnt count on the quality of these elctrodes over a wide pH range. They should be tested and verified. They are most likely indicating near correct pH in a vary stable solution and not very responsive over a large range ( in other words they're currently zeroed into reading correctly and wont if the solution varies a lot). The failure rate after 2 months maybe the case with electrodes that have been on a shelf for long periods beore being commissioned for use or less likely but I have seen it - a bad "batch" of electrodes you received from stock. Consult your supplier for support. If these are being used in low temperature conditions (under say 45 degrees F) you may require thermal compensation to read correctly over the 32-45 degree range.
542085
Shanna and Geo06 have got this just about right.  The only thing I can add is that radiocarbon dating can not be used for more than about 70,000 years ago, and is more accurate for living things that died within the last 8,000 years.\n\nMost geologists measure rock ages in millions, or even billions, of years, so the age of the earth and the age of almost all igneous rocks is well beyond the range of carbon dating.  On top of that, igneous rocks contain very little if any carbon,  so carbon dating is not applicable here.  \n\nSo the only thing carbon 14 can be used for is to determine the time that an exchange of carbon with the atmosphere stopped, ie, the death of a living thing - the third item on your list of choices for your homework.\n\nThe half life of C-14, the radioactive isotope of carbon, is about 5730 years.  Therefore, if you know the ratio between C-14 and C-12 in the atmosphere when the organism died, and you know the ratio now, the difference in the ratio can be calculated backwards, using the half life, to estimate when the organism died. \n\nAtmospheric C-14 has not been in a constant ratio with C-12, as previously thought, so there are some serious problems with the accuracy of C-14 dating.  The problem is that the natural ratio of the carbon isotopes in the atmosphere (carbon dioxide) varies because cosmic ray bombardment of the outer atmosphere produces C-14 but not C-12.  The ratio can be predicted accurately using the ratios in old trees, where the tree rings can be used to accurately determine the age of each ring with its annual ratio, with a maximum of about 8,000 years -that's how old the oldest trees are which can establish a reference ratio.\n\nDating of artifacts is a best guess, the best method is to measure the amount of lichens growing on them, or the age of carbon in ashes found in the same spot.
448024
They were right to, though maybe for the wrong reason\n\nC14 has a half-life of only 5700 years.  Which means that if you are testing anything, more than, say, 100,000 years old, there is not enough C14 for you to assay accurately.  Dinosaurs died out 65,000,000 years ago.  There are other dating methods you can use, but not C14.\n\nSecond, C14 only works on things that were once alive, like bones, or wood.  You would never use it directly on a footprint, though maybe you could test something that you found at the same strata, and therefore had reason to think was the same age as your footprint.\n\nIf you want a good, scientifically accurate article about radiometric dating, the following was put out by an association of scientists who are also Christians.\n\nhttp://www.asa3.org/aSA/resources/Wiens.html
324633
Yes! The proton has a half life estimated by the electroweak theory to be about 10^32 years.\n\nThis means that in our lifetime, or probably ANY human being's lifetime, there will be no effect, because the half life is so large.\nYou's have to wait trillions of years to see even a remote difference.\nEventually, though, the universe will end up as a big jumble of fermions. (I'm assuming that bosons are unstable, and fermions (like the electron) are stable. Correct me if i'm wrong, someone!)\n\nParticle physicists are currently looking for experimental evidence of proton decay to validate the elctroweak theory (the unification of the electromagnetic and weak forces).
85947
The half-lives will vary depending on the isotope.  Go to the library and look them up in "The Handbook of Chemistry and Physics" in the reference section.
170518
They can't use carbon dating for that. They use other materials...I think Phosphorous is what they use. If you want to know how it works what they do is they "count" the number of an atom's isotope remaining then plug it into the half-life forumula (I foget what it is, but it has a log in it somewhere) and then they get the age of the material.
529317
It is very simple.  This method will help you when the fraction is not a nice one like 1/16.\n\n\nAt time zero you have, let's say N0 = 1600 atoms of protactinium-234.  After 26.76 hours, 1/16 remain:\n\nNt = 1600 / 16 = 100.\n\nNow in radioactive decay:\n\nNt = N0 * exp (-Lamda * t).\n\nYou have t, Nt, N0.  Calculate lambda\n\n100 = 1600 exp (-Lambda * 26.76)\n0.0625 = exp (-Lambda * 26.76)\nTaking Ln on both sides\nLn 0.0625 = - Lambda * 26.76\nLambda = - (Ln 0.0625) / 26.76 = 0.10361 h^(-1)\n\nHalf life = (Ln 2) / Lambda = 6.69 hours
375757
the definition of 1/2 life is that 1/2 of the material will be left after that amount of time.\n100 g to start, 50 g after 1 half life.\n25 g after 2 half lives.\n\nb) 60 yrs is 2 half lives.  see ans to part A)\nc) 25 g will be left after 60 yrs.  See answer to part A)\n-->
264504
Radium half life is 1602 years...\nso if we may consider it to be 1600 years than after 1600 years you will find approx. half of the radium left in the container = 0.5 kg\nafter 4800 years = 3 x half life ... in the container there remain about 1/8 of the original mass,  = 0.125 kg\n\nbut if you want to calculate exactly there is the radioactive decay law, see http://en.wikipedia.org/wiki/Half_life
103861
You can use them for neutralizing waste before discarding, but for analytical work they should be replaced.  Shelf lifes vary but one year should be a good max for prepared reagents and five years for solids and concentrates.  This of course varies based on the particular chemical and usage.    Of course, if there is any question, discard.