Asked by lolo
How long will it take for the 100mg of cesium-137 to decay to 6.25mg(1/16 the original amount)?
Answers
Answered by
DrBob222
2<sup>n</sup> = 16
Solve for n = number of half lives.
Solve for n = number of half lives.
Answered by
lolo
still i can't understand it
Answered by
DrBob222
Do you have the half-life given in the problem or are you allowed to look it up? If so there is an easier way to set it up.
To solve 2<sup>n</sup> = 16, take the log of both sides.
log 2<sup>n</sup> = log 16
n*log 2 = log 16
n*0.301 = 1.2 etc.
There is another way. Remember that half-life means the time it takes for 1/2 the material to disappear. So make a table like this. The periods are used for spacing.
amount......# half-lives
100 mg.........0
50 mg..........1
25 mg..........2
12.5 mg........3
6.25 mg........4
So whatever the half-life is, multiply that by 4 and you will have the time it takes to go through 4 half-lives.
To solve 2<sup>n</sup> = 16, take the log of both sides.
log 2<sup>n</sup> = log 16
n*log 2 = log 16
n*0.301 = 1.2 etc.
There is another way. Remember that half-life means the time it takes for 1/2 the material to disappear. So make a table like this. The periods are used for spacing.
amount......# half-lives
100 mg.........0
50 mg..........1
25 mg..........2
12.5 mg........3
6.25 mg........4
So whatever the half-life is, multiply that by 4 and you will have the time it takes to go through 4 half-lives.
Answered by
Anonymous
thanks alot , this answer really helped me to understand this question
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