physics halflife

izzi_xox

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if i was asked what the definition of half-life is, would I say it is the time taken for the number of nuclei in a sample to halve, or would I say it is the time taken for the count rate/activity in a sample to halve from its initial rate?

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chinua achebe

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either:
-average time taken for a substance to decrease by half in terms of activity
or
-average time take for half of the radioactive atoms to decay

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princesslife

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it can be either:

avg time it takes for number of nuclei of isotope in a sample to halve
OR
avg time it takes for count rate from sample containing isotope to fall to half of its initial level

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bilalsheraz7

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No just say

Half life is the term given to describe the amount of time (on average) it takes for the number of unstable nuclei in a radioactive sample to half

Radiation dose: a measure of the risk of harm

Affected by which organs radiation is exposed to
What type of radiation you’re exposed to
Amount of radiation your exposed to
Existing health problems eg skin issues Tukka akhi

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triga12345

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(Original post by chinua achebe)
either:
-average time taken for a substance to decrease by half in terms of activity
or
-average time take for half of the radioactive atoms to decay

^^

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bilalsheraz7

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(Original post by triga12345)
^^

What do u think the grade boundaries will be

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RainDancess

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40-5
38-6
50-7
62-8
78-9
just my opinion

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triga12345

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(Original post by RainDancess)
40-5
*38-6*
50-7

um what? im going to assume you meant 48-6 but do you really think 6-7 will be split by 2marks/?

9-?
8-71
7-63
6-56
5-49
4-41

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RainDancess

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(Original post by triga12345)
um what? im going to assume you meant 48-6 but do you really think 6-7 will be split by 2marks/?

9-?
8-71
7-63
6-56
5-49
4-41

no point in trying to guess lol, it wont be 90% for a 9 like some people say on here tho i reakon it wont be much more than 50 for a 7

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LarissaAlves

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this is from BBC bitesize

The nuclei of radioactive atoms are unstable. They break down and change into a completely different type of atom. This is called radioactive decay. For example, carbon-14 decays to nitrogen-14 when it emits beta radiation.
It is not possible to predict when an individual atom might decay. But it is possible to measure how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope.
Two definitions

There are two definitions of half-life, but they mean essentially the same thing:

the time it takes for the number of nuclei of the isotope in a sample to halve
the time it takes for the count rate from a sample containing the isotope to fall to half its starting level

Different radioactive isotopes have different half-lives. For example, the half-life of carbon-14 is 5,715 years, but the half-life of francium-223 is just 20 minutes.

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