5 Things You Dont Know About Radioactivity

You lot are using an out of appointment browser. It may non display this or other websites correctly.
You should upgrade or apply an alternative browser.

• Forums
• Physics
• Loftier Energy, Nuclear, Particle Physics

Uncomplicated question virtually radioactivity

• Thread starter aviv
• Commencement date Dec 9, 2003

What makes nuclei disintegrate at a certain signal in time as opposed to another? As in, what is the fundamental reason for disintegration finally happening in an unstable nucleus?

Answers and Replies

Information technology's completely random, but the probailty that a nucleus decays can be affected by external factors.

Alpha decay can be reduced to the proabilty of the alpha particle (which can be thought of as reatining it'southward identity even when it is part of the nucleus) tunelling (equally in quantum mechanical tunelling) out of the potential well casued by the stiff nuclear forcefulness. The about obvious factors which would touch on the proabilty of the blastoff particle tunelling out of the nucleus is the potential involved.

I would hold with jcsd. To rephrase his statement, I would say information technology is a consequence of the wavefunction. Both the weak and strong forces have to play a part in it considering the strong forcefulness will concur the nucleus together very strongly. I would say that the decay must happen through i of at least three modes:

1) quark flavour decay: a quark in ane of the constituent nucleons changes season, every bit in the neutron decay n --> p + e- + -v. This manner accounts for beta decay, electron capture, and a small fraction of gamma disuse.

ii) radiative disuse: nucleons moving to lower energy states in the nucleus emit a gamma photon. This manner accounts for the bulk of gamma decay.

iii) tunneling decay: the wavefunction of a particular slice or elective of the nucleus allows it to tunnel out of the nucleus sufficiently far to escape. This way accounts for some neutron emmission and alpha disuse.

I'm sure there are more, and that I oasis't covered half of what could proceed, simply these are some of the nuts in nuclear decay. I am not entirely sure how massive nuclear fission occurs exactly, merely I would also guess that information technology results from a moving ridge-function linked to nucleons trying to settle into more suitable free energy levels afterward neutron capture (as in Uranium 235 + north --> Uranium 236 --> fission products).

So what if we magically figure out the energy levels and all the backdrop of an unstable nucleus at a sure time (I know this is impossible only but for the sake or argument). Could we then predict the exact time of decay of that nucleus?

Originally posted by aviv
So what if we magically figure out the energy levels and all the properties of an unstable nucleus at a sure time (I know this is impossible but merely for the sake or argument). Could we then predict the exact time of decay of that nucleus?

The randomness is an intrinsic part of the system, you take a wavefunction which behaves in a perfectly deterministic way which can correspond to a unmarried known energy level and a known potential, just when you go to make a measurment you'll always find that that there is a ceratin probabilty that decay has occured.

I'll just add with specific reefrnce to alpha decay:

the wavefunction [itex]u_n(x)[/itex] ([itex]due north[/itex] corresponds to the energy level of the alpha particle)as I said behaves in a perfectly detrministic way, merely imagine in the example where we have our Alpha particle still inside the nucleus (at to the lowest degree last time we looked) and nosotros haven't however fabricated a measurement, the wavefunction, though it is centred on the nucleus reaches exterior the nucleus through the potential bulwark (where it decays exponmentially)and out of the other side into the region where the coaction of the bonny potent force and the repulsive Coulomb force would allow our blastoff particle to be at it's present energy level. The wavefunction at a certain indicate at a sure correspondfs to the probailty of finding our alpha particle at that point at that time via the relationship:

[tex]|u_n(10)|^2 = P(x)[/tex]

So when we make a measuremnt in that location is always a probailty that we can notice the blastoff particle exterior of the nucleus.

Originally posted by jcsd
The randomness is an intrinsic function of the system, yous have a wavefunction which behaves in a perfectly deterministic way which can correspond to a single known energy level and a known potential, but when you go to make a measurment you'll always find that that there is a ceratin probabilty that disuse has occured.

And then what you are maxim that the time of disuse is not predictible just when you lot insert measurement. That if I was a being that knew all that was going on at the present, I could predict the exact time a certain nucleus volition decay. And that information technology is but when yous bring in the states humans trying to measure out the situation that you get this probability situation.

Am I right?

thank you in advance

No, it'southward deeper than that before you brand a measurement of it's postion the alpha particle doesn't take a well-defined postion (you could say it has simultaneously inside and outside of the nucleus, only that's not the conventional interpretation), the act of measutremnt forces the nucleus to decide whether information technology has decayed or not.

Originally posted by jcsd
the deed of measutremnt forces the nucleus to decide whether it has rust-covered or non.

How so?

And, do y'all mean that until measured, the alpha particle has no real position and that it only gets a position one time measured?

Aye that'south exactly what I hateful, this may seem counterintutitive, but quantum physics isn't intutitive.

What happens when you make a measuremnt is that the wavefunction collapses at random into one of information technology's eigenvalues.

Cheers a lot that clears upwards a few things.

I yet don't understand a hell of a lot well-nigh this, like how exctly "the human activity of measutremnt forces the nucleus to make up one's mind whether it has rust-covered or not" merely I still take many many many years to effigy it out

Cheers again.

I wouldn't worry nearly it as why the wavefunction colapses when a measuremnt is made has baffled people for years; it's called te breakthrough mechanical measurment problem. The phenoumna of decoherence and alternatiove interpretations of quantum mechanics do try to adress this problem though.

Originally posted by aviv
I still don't understand a hell of a lot almost this, like how exctly "the deed of measutremnt forces the nucleus to make up one's mind whether it has decayed or not" ...

I wouldn't feel too bad about your level of agreement. If I'm non mistaken, Einstein didn't even ever come to understand (or even take) it.

Originally posted by aviv
And then what if we magically figure out the free energy levels and all the properties of an unstable nucleus at a sure time (I know this is impossible just but for the sake or argument). Could we so predict the verbal fourth dimension of decay of that nucleus?

Effort this analogy on: You have a ball bouncing around in a box with an opening in it. It bounces effectually completely randomly. You lot know how big the ball is, how big the opening is, and how fast its moving around. From this you lot can calculate the average time information technology should take to find the opening, but you volition never exist able to caclulate exactly when it will find the opening.

I think Einstein understood it, but he certainly never accepted information technology.

The illustration of ball bouncing around a box (presumably in a non-linear way) is okay, only information technology suggests that the particle has a postion earlier it is measured, though there are realist intrepretaions (e.g. Bohm's) where the partcile does take a postion before it'south measured, it'south non the conventional interpreation of quantum mechanics.

Originally posted past jcsd
I retrieve Einstein understood it, but he certainly never accustomed it.

He understood it more than I practice, probably, but, when someone thinks a consummate theory is incomplete for the wrong reasons, then can you actually say that that person understands it?

Originally posted by jcsd
... there are realist intrepretaions (e.grand. Bohm'south) where the partcile does accept a postion before it'southward measured, ...

Doesn't the Bohm-DeBroglie interpretation have holes in it, similar conservation bug?

Thanks everyone. I still don't like the idea of a particle having no position until measured considering if information technology has no certain position then how can it be in a certain position once measured, or to be measured? Same with a particle colliding, how tin a particle collide in a certain position when it had no certain position before the standoff? This is very interesting, I'thou gonna read about Bohm's interpretation.

Originally posted past turin
He understood information technology more than I practise, probably, just, when someone thinks a complete theory is incomplete for the wrong reasons, then can you really say that that person understands it?

Well I think if he didn't empathise it he wouldn't of been able to come up with all his diverse attempts to disprove it (i.due east. EPR paradox, etc.), which really helped to accelerate quantum mechanics. I don't think yous have to necessarily believe something is truthful to understand information technology.

Doesn't the Bohm-DeBroglie estimation have holes in information technology, like conservation problems?

It's got bug like the not-locality of the quantum potential, a particle in it desn't seem o have whatever other real attributes rather tthan postion, etc. And then well-nigh people pass up it. I thikn information technology simply illustrates the problems of trying to create a realist interpretation of quantum mechanics.

Originally posted past aviv
Thanks anybody. I still don't like the idea of a particle having no position until measured because if it has no sure position and then how tin it be in a sure position once measured, or to be measured? Same with a particle colliding, how can a particle collide in a certain position when it had no certain position before the collision? This is very interesting, I'm gonna read nigh Bohm's interpretation.

Considering it has a probailty of having a sure postion one time a measuremnt is made.

I wouldn't bother with Bohm'south interpretaion, information technology's interesting, bu it'south unlikely to ever be more useful than or to replace the conventional interpretaion of quantum measurement, I were you I'd wait at decohernce or Everett'due south/the many worlds interpretation equally they give much more than satisfactory answers than Bohm.

Originally posted past jcsd
I were you I'd wait at decohernce or Everett's/the many worlds interpretation every bit they give much more than satisfactory answers than Bohm.

Thanks, will do!

Related Threads on Simple question about radioactivity

• Terminal Post
• Mar 30, 2014

• Last Mail service
• Jun 10, 2016

• Final Post
• Jun 7, 2012

• Last Post
• Oct 25, 2004

• Terminal Mail service
• Sep 8, 2004

• Last Post
• Sep x, 2008

• Last Post
• Dec 11, 2010

• Concluding Mail
• Jul 31, 2015

• Terminal Post
• December 1, 2009

• Last Post
• Aug 5, 2004

• Forums
• Physics
• Loftier Free energy, Nuclear, Particle Physics

carrollmoste1948.blogspot.com

Source: https://www.physicsforums.com/threads/simple-question-about-radioactivity.10594/

Share this post