Why can't X-Rays travel through water?

[nst.john]

I read that X-Rays cannot travel through water and I wanted to understand why. What happens when X-Rays and water molecules interact that prohibit X-rays from traveling within water?

 

[mathman]

http://www-als.lbl.gov/index.php/holding/167-isotope-and-temperature-effects-in-liquid-water-probed-by-soft-x-rays.html
Above describes interactions between x-rays and water. Water is not opaque to x-rays.

 

[Vanadium 50]

I read that

And you aren't going to tell us where, so we can't then look it up and find out what they are talking about?

You are mostly water. If water were opaque to x-rays, you would be too. Does this sound right to you?

 

[nst.john]

That is true. And it was in this paper on sonoluminescence. http://www.physics.ucla.edu/Sonoluminescence/sono.pdf

 

[nasu]

Where do they mention x-rays in that paper? Can you indicate at least the page?

 

[SteamKing]

Where do they mention x-rays in that paper? Can you indicate at least the page?

It's on the last page, left hand column, the paragraph immediately preceding "Noble Addition".

 

[davenn]

OK so they are referring to Soft X-rays not traveling through water which is basically correct

medical X-rays are "Hard" X-rays ( higher frequency)

http://www.genesis.net.au/~ajs/projects/medical_physics/x-rays/

The clinical application of X-rays to form images
Hard and soft X-rays
Hard X-rays are X-rays with a higher frequency and are more penetrating than soft X-rays. Soft X-rays are usually filtered when doing a scan because they can't penetrate through a patient's body and add needless risk of radiation damage.

Dave

 

[nst.john]

Okee doke thank you for the clarification. But why can't soft xrays propagate through water?

 

[M Quack]

At reasonable^* photon energies the main interaction between x-rays and matter is through the photoelectric effect: The photon gets absorbed by an atom and produces a free electron and a "hole" in the electronic configuration of the atom.

The photoelectric cross section decreases very fast with the photon energy, i.e. low energy, soft x-rays are absorbed much stronger than high-energy, hard ones.

In practice this means that x-rays with E<1keV cannot penetrate a sheet of paper whereas hard x-rays with E>50 keV can go through a lot of stuff - several centimeters of water, bones, even steel, rocks, etc.

Visible light, IR and so on can travel through some materials if the photon energy is smaller than the band gap/smallest binding energy of the material. In that case the photons do not have enough "punch" to produce an electron-hole pair.

http://en.wikipedia.org/wiki/Photoelectric_effect

^* "unreasonable" according to this definition starts at a few 100 keV