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A sample of a radioactive substance decayed to 95 percent of its original amount after a year.what is the half life of the substance?
Wiki User
∙ 14y ago
The half-life of a radioactive nuclide when 95% of it is left after one year is 13.5 years.
AT = A0 2(-T/H)
0.95 = (1) 2(-1/H)
ln2(0.95) = -1/H
H = -1/ln2(0.95)
H = 13.5
Wiki User
∙ 14y ago
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How much of radioactive substance remains after 15 hours if it's half life is 5 hours?
The half-life of a radioactive substance is the time that it takes for half of the atoms to decay. With a half-life of 10 days, half has decayed in this time. After 20 days, a further 10 days/another half life, a further half of the remainder has decayed, so 1/4 of the original material remains, 1/4 of 15g is 3.75 grams. This is the amount of original radioactive substance remaining, but it’s daughter isotope ( what the decay has produced ) is also present, so the original sample mass is effectively constant, especially in a sealed container. Even in an unsealed container, and assuming alpha ( helium nucleii) emission, a drop in mass per radioactive atom of 4 Atomic Mass units, compared with the original atom of, say 200 amu is only 2% mass decrease, less for heavier decaying nucleii.
Is the quantity of a radioactive isotope ever equal to exactly zero?
Yes. There are isotopes of elements that are simply not found anywhere in the universe (and even if they did exist momentarily, their lifetime is so short that in the next moment they would have decayed into a different more stable isotope).
Where can you find pictures of decayed teeth?
Here is a picture of some tooth decay: http://www.icfcd.com/decayed-teeth.html
Best definition of half-life for a radioactive substance?
The half-life of a radioactive substance is the time it takes for half of the atoms in a sample to decay. It is a constant characteristic of each radioactive isotope. After one half-life, half of the original substance will remain, and the other half will have decayed into other elements.
How much of a radioactive substance remains after 10 hours if its half life is 5 hours?
After 10 hours, 25% of the radioactive substance remains because each half-life reduces the amount by half. So, after the first 5 hours, 50% remains, and after the next 5 hours, half of that amount remains, which is 25%.
Why is radioactive waste considered safe after 10 half lives?
I would consider it safe after 5 half-lives. by 5 it has decayed to 3% of original level, by 10 it has decayed to 0.1% of original level.
Why will the amount of a radioactive substance never reach zero amount present?
Radioactive decay is a random process, and there is always a chance that a nucleus will decay over time. This means that even if the amount of a radioactive substance becomes extremely small, there will still be some nuclei that have not yet decayed. As a result, the amount will never reach exactly zero.
How much of radioactive substance remains after 15 hours if it's half life is 5 hours?
The half-life of a radioactive substance is the time that it takes for half of the atoms to decay. With a half-life of 10 days, half has decayed in this time. After 20 days, a further 10 days/another half life, a further half of the remainder has decayed, so 1/4 of the original material remains, 1/4 of 15g is 3.75 grams. This is the amount of original radioactive substance remaining, but it’s daughter isotope ( what the decay has produced ) is also present, so the original sample mass is effectively constant, especially in a sealed container. Even in an unsealed container, and assuming alpha ( helium nucleii) emission, a drop in mass per radioactive atom of 4 Atomic Mass units, compared with the original atom of, say 200 amu is only 2% mass decrease, less for heavier decaying nucleii.
When three-quarters of a radioactive isotope has decayed to become the stable daughter product how many half lives have occured?
When three-quarters of a radioactive isotope has decayed, it means that 1/4 (or 25%) of the original isotope remains. This corresponds to 2 half-lives, because each half-life halves the amount of radioactive material remaining.
What part of a radioactive sample remains unchanged after 2 half lives?
After 2 half lives, 25% of the original radioactive sample remains unchanged. This is because half of the sample decays in each half life, so after 1 half life, 50% has decayed, and after 2 half lives, another 50% has decayed, leaving 25% unchanged.
How is radioactive decay used to determine the absolute age a rocks?
The basic idea is to measure the amount of the radioactive isotope, and of one or more of its decay products. The older the rock, the larger the percentage of the original isotope that decayed - so the ratio between the original isotope and the decay product changes over time.
After two half-lives, how much of the original material has decayed?
After two half-lives, 75% of the original material has decayed.
What is the destiny of neptunium?
Being radioactive neptunium is decayed down to a stable isotope.
What is the stable isotope that is formed by the breakdown of a radioactive isotope?
The stable isotope formed by the breakdown of a radioactive isotope is called a daughter isotope. This process is known as radioactive decay, where a radioactive isotope transforms into a stable daughter isotope through the emission of particles or energy.
How much of a radioactive substance remains after 24 hours if its half life is 5 hours?
Using the formula Nt = N0*(1/2)t/t1/2 where Nt is the amount of stuff remaining after an amount of time, t, and t1/2 is the half-life, you get Nt = .036N0. So about 3.6% of the radioactive stuff is left.
