Why can wireless internet signals pass through walls when visible light cannot?

[evk]

Hi, the title above is a specific instance of a more general question. I'm basically wondering why the atoms in a wall would prevent visible light from passing through, yet allow both X-rays (which are HIGHER frequency) and radio waves such as 802.11b wireless internet (which are LOWER frequency) to pass through.

What's going on in the interaction between the atoms in the wall and the photons of various frequencies that allows both a higher and a lower frequency light to pass through, while still stopping visible light?

Thanks!

 

[Ratzinger]

http://hyperphysics.phy-astr.gsu.edu/hbase/mod3.html#c1

that's why

 

[Danger]

Neat link, Rat. Thanks.

 

[evk]

Thanks!

That was exactly what I wanted. Thanks a lot!

 

[azzkika]

referring to the link explaining xrays down to microwaves, it says that if a strong enough light is shone on a hand then the 'red' frequency of light is not absorbed, but can be seen through the hand.

now in another thread i asked why light doesn't travel through voids in atoms and also the differing properties betweem transparent and none transparent atoms. as far as i could ascertain, light interacts with the atom and the escaping light is not that what hit the atom, but what the atom itself generated in reaction to light hitting it. and when the out going frequencies match the incoming ones, that is what causes transparency. so you when you look through glass you don't see the light from outside, rather the light that the glass atoms are emitting due to the light hitting the glass.

is this the case for all transparency?? ie, the redness seen through a hand under strong light, is light emitted from atoms within the hand rather than the 'red' frequency traveling through??

and just out of curiosity, do atoms interact with all EM frequencies in this way, ie transparency to any EM is merely the atom generating an outgoing frequency the same as the incoming one??

 

[anant25121986]

Regarding the question about transparency... vacuum is transparent... no absorption/scattering is observed due to lack of atoms and molecules... in a medium however, the atoms may absorb and emit EM rays as stated... there is also a chance of bending of light waves if the obstacle's size (in this case that of the atoms/molecules) is comparable to the wavelength of the wave... Radiowaves have large wavelenghts and can bend over buildings... i hope this helps u out...