Why are beta particles less penetrating than x-rays?

Smythe

Why are beta particles less penetrating than x-rays?

ray giraffe

A bit of Googling led here: http://www.tesec-int.org/TechHaz-site%2008/Radiation-interaction.pdf

Short Summary:

Beta particles are charged and so interact with orbital electrons.

Higher energy x-rays penetrate much more than lower energy x-rays.

Lower energy "soft" x-rays in fact penetrate very little.

X-Ray Penetration is related to the photoelectric effect and compton scattering.


That's not a very convincing explanation to me, maybe someone else can do better?

krd

Here's my go.

I think it's because the β particle has a charge. It will be attracted to any molecules or atoms with an opposite charge - causing it to smash into them.

The photons of the x-ray have no charge - they can move further through empty space without hitting anything.

Smythe

krd wrote: »

β particle has a charge. It will be attracted to any molecules or atoms with an opposite charge - causing it to smash into them.

From what I've read, approaching electrons only see the outer charges of molecules and atoms. Considering the sign of the charges involved, there is no attraction. If they are going fast enough there will be some crashing.

The lack of charge does enable the x-rays to make it through materials, too.

thecornflake

I haven't looked into it much but perhaps it also has something to do with the scattering cross section ?

krd

Smythe wrote: »

From what I've read, approaching electrons only see the outer charges of molecules and atoms. Considering the sign of the charges involved, there is no attraction. If they are going fast enough there will be some crashing.

The lack of charge does enable the x-rays to make it through materials, too.

Honestly, I don't really know. It disappears into the world of quantum voodoo. Which I don't really have a proper understanding of.

The x-rays are absorbed in relation to the density of electrons in a material.

Hmmmm.....the more I think about this the more problems present themselves. I know what I've observed, but that doesn't really give the answer "why".

Someone who might know their quantum mechanics, might say the β particle has a higher probability of hitting something sooner than the x-ray. But that would be like me saying, the β particle is likely to hit something sooner than the x-ray.

I would say the x-ray can penetrate a material further, because it's wavelength is so short, it can go further without bumping into anything . But how that confuses me is how radio waves can also penetrate solid material - unless it's something like quantum tunnelling - which I don't really understand either (because it conflicts with other things, I'm trying, to understand). And the things the x-ray collide with, what are those things?

I can tell you like charges will repel, and opposite charges will attract, but I don't know why they do that.

Just from some brief reading today: if an x-ray hits and atom, an electron can be emitted. If an electron hits an electron, an x-ray can be emitted.

citrus burst

Its down to charge and electromagnetic interactions. Beta particles have a charge of +/- 1 (positrons or electrons). X rays are photons and have no charge. When a beta particle enters a materiel, it is effected electromagnetically by the charged particles (protons and electrons) in the material. This causes them to interact with the surrounding atoms and usually results in the emission of radiation.

X rays on the other hand do not interact with the charged particles unless they collide with them (see Compton scattering) so can penetrate a materiel much more then beta particles.

It's slightly more complicated then that in reality, involves solving a few tough equations, but roughly speaking its due to the charge of beta particles that makes them less penetrating then x rays. Hope this helps.

thecornflake

citrus burst wrote: »

Its down to charge and electromagnetic interactions. Beta particles have a charge of +/- 1 (positrons or electrons). X rays are photons and have no charge. When a beta particle enters a materiel, it is effected electromagnetically by the charged particles (protons and electrons) in the material. This causes them to interact with the surrounding atoms and usually results in the emission of radiation.

X rays on the other hand do not interact with the charged particles unless they collide with them (see Compton scattering) so can penetrate a materiel much more then beta particles.

It's slightly more complicated then that in reality, involves solving a few tough equations, but roughly speaking its due to the charge of beta particles that makes them less penetrating then x rays. Hope this helps.

That sounds correct. Coulomb and all that jazz.