Why do we want to about half life instead of its full life?

Question

In terms of radioctivity why is it more important to know about the half life of radioactivity?

Answer 1

Suppose you are given 10,000 $ and are permitted to spend half the amount every day, in how many days you will spend the entire amount?

First day ½ = 5000$ remaining 5000$

Second day ½ of the remaining 5000$ = 2500$ that is (1/2) ^2 of 10,000 $. Now remains only 2500

Third day ½ of 2500$ = 1250 $ that is (1/2) ^3 of 10,000 $. Now remains only1 250


In the nth day you will spend (1/2)^n of 10, 000 $. Remaining
{10 000 -(1/2)^n of 10, 000 $}.

Only when n approaches ∞, the remaining approaches zero.

There are natural processes which decay exponentially like the above.

In the above example half life period is one day.

If you were allowed to spend half of it every two day, then the half life period is two days.

If you are allowed to spend every year like this, the half life period is year.

Note that there is no full life period.

Answer 2

Half life is the time if takes for half of the matter to have decayed. It is unknown how long it takes for it all to go, because the half life is an average, the last atom may take longer to decay. If there was 10 atoms, and after a minute there were only 5 the half life is 1 minute. But after another minutes there would be either 2 or 3 atoms left which has not decayed. Also by knowing the full life on the element you cannot apply it to different quantities. Using the same example; 10 atoms (half life 1 minute) would take approximately 3 minutes to decay, where was having 30 atoms means it would take approximately 4 minutes to decay. As you can see this is not an a "even" scale. I hope you understand this

Answer 3

O M G OF COURSE IS A STUPID QUESTION... dear god how can somebody... oh no... no... the humanity... think in the children... oh and half life only depends on the material so it doesn't mater if you have 1 pound or 1 ton of uranium 235 in 4000 million years half will be gone and every radioactive material has its own half life defined by an exponential equation until everything becomes lead the more stable of all elements

Answer 4

Because half life is not what you think. Half life does not mean that a radioactive particle still have to live "this much". It means that if you have a number of radioactive particles of the same kind, after a time equal to the half life you still have half of those particles not decayed. After another half life, half of those will have decayed (thus you have 1/4 of the initial number of particles after two half-lives).

The half-life is actually a measure of the probability for a probability of the particle to decay; you can't predict when it will decay, only the probability that it will decay after a given time (usually described as the fraction of particles that will decay in a fraction of time). It is still possible to have non-decayed particles left even after many, many half-life times.

Answer 5

It is impossible to determine the "full" life of a radioactive material without first determining it's halflife. If the halflife of a material is 1 year, then after 1 year half of the material would be inert...then after 1 more year half of the half would be inert...and so on

For 1kg of material, after 1 year 500mg would be active, then after 1 more year 250mg would be active and after 1 more year 125mg would be active...

This is the easiest way to find out how long a supply of radioactive material will remain radioactive.

It is the same with medications. that is how drug manufacturers determine how long a drug will remain effective in the body.

Answer 6

The half life of a substance is related to the rate of decay and radioactivity. It is also helpful in determining many other quantities and information.

Answer 7

it so happens that a radioactive element will lose half of its original mass in a certain time interval.so if the element is 1kg in mass,and has a half life of 1s then
after 1s mass=0.5kg
after 2s mass=0.25kg
after 3s mass=0.125kg
after 4s mass=0.0625kg
after 5s mass=0.03125kg
and so on
its mass will consistently dissipate but will not completely disappear.hence it is practically impossible to know the "full life"of a radioactive element.therefore we use the half life to study about it.

Answer 8

I think I understand, and I think the answer might be that since the decay rate is exponential if we were to find the full life we would be going to infinity... So instead we just find its half life since its something we can calculate... Not sure if thats right tho

Answer 9

i think the half life point refers also to its peak of consequential destruction and after this point the effects gradually become less until it is no longer deadly.

im not scientist, just my opinion which seems logical :)

Answer 10

because it's the most important part of it!