114 votes

Why is radioactive half-life constant?

It might help you think of it in terms of tossing coins or rolling dice. Say you toss a bunch of coins every minute and get rid of all the ones that turn up tails. The coin collection would have a ...
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  • 7,529
57 votes

Why is radioactive half-life constant?

It doesn't work on something like 4 atoms, or even a hundred atoms. It's statistical so you need many many atoms. What you are doing is like calculating the derivative to find the slope at one point ...
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  • 7,720
25 votes

Why is radioactive half-life constant?

It's almost as if the atoms in a sample somehow 'know' how many other atoms are in the sample. This is the key. It is actually exactly the opposite, it is precisely because they don’t know how many ...
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14 votes

Why is radioactive half-life constant?

Say you have just 4 radioactive atoms with a half-life of 1 hour. . . . . . So that means 1 hour from now, 2 of the atoms will have decayed (on average) and 2 will remain undecayed (on average). That ...
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  • 79.6k
12 votes

Why is radioactive half-life constant?

Atoms only have a few distinguishing properties like the number of protons, neutrons, electrons and their energy levels. Atoms which have these same few properties are identical and indistinguishable ...
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7 votes
Accepted

Is diamond a good neutron moderator?

If the wavelength of a neutron is much shorter than the distance between atoms in a material, then the approximation that the neutron is interacting with the entire crystal collectively doesn't really ...
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7 votes

Why is radioactive half-life constant?

Afterall, if it took 1 hour for the first 2 atoms to decay, then surely it should take 1 more hour for 2 more atoms to decay. Believe it or not, I started the same thought experiment at the exact ...
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7 votes

Why is radioactive half-life constant?

Let us suppose you have a kilo of some radioactive element. After time equal to the half life you now have half a kilo of said radioactive element left (plus the decay products of the other half kilo)....
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  • 1,089
6 votes

Why is radioactive half-life constant?

This overlaps other answers but maybe the different phrasing will suit you. Suppose that it worked as you expected then odd things would happen. Suppose you have $4$kg of radioactive stuff with a ...
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  • 1,959
4 votes

Why is radioactive half-life constant?

Radioactive decay is a random process at the level of single atoms. A nucleus of a radionuclide has no “memory”. A nucleus does not “age” with the passage of time. Thus, the probability of its ...
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  • 51
2 votes

Why is radioactive half-life constant?

Labelled and Unlabelled Atoms Afterall, if it took 1 hour for the first 2 atoms to decay, then surely it should take 1 more hour for 2 more atoms to decay... You propose two situations There are 4 ...
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  • 269
1 vote
Accepted

Find the maximum possible energy for a beta-particle decay-chain

Yes. (Some questions are easy to answer :) )
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1 vote

Radiation pressure at a oblique surface

The photon momentum is $p = \frac{h}{\lambda} = \frac{E}{c} = \frac{u \cdot \Delta V}{c}$ with $u$ being the energy density and $\Delta V$ is the volume given. And the Intensity $I$ is the energy ...
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1 vote

Why is radioactive half-life constant?

The universe is ultimately quantum mechanical, and does not care about our classical way of thinking. Every single atom in your sample has the same exact probability of decaying, and this is because ...
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1 vote

Why is radioactive half-life constant?

It is useful to recall what is actually going on in an atomic nucleus. The below is highly oversimplified, but serves to give an intuitive feel for roughly what is going on inside a nucleus. You have ...
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1 vote

Why is radioactive half-life constant?

As other answers have pointed out, the half-life of a substance is based on probability. A particle has a certain probability that it'll decay at any given moment. If you have 200 particles with a 1/...
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1 vote

Why is radioactive half-life constant?

I feel that everyone is getting a little off topic and too elaborate with their answers. They also aren't answering the question which is why did the two items not decay in that 1 hour time. The ...
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  • 11
1 vote

Why is radioactive half-life constant?

The kinetics of irreversible processes (chemical reactions, deformation, heat flow, etc) are not always linear, i.e. the second half of the process won't complete as quickly as the first. In general ...
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  • 229
1 vote

What range of light on the electromagnetic spectrum are produced by the de-excitation of electrons?

I’m going to cheat a little and suggest rather than just considering transitions of electrons between bound states that you can also consider radiation form electrons being accelerated or suddenly ...
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  • 1,561
1 vote

Confusion about Length Contraction (ex in Muon decay)

Useful to add maybe that the apperance of relativistically moving objects can be quite the opposite of length contraction. This is caused by Terrell rotation. This answer is a substitute for a comment ...
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