first off i don't have a clue about physics. ok with that established, here's my question

how come radiowaves can go through walls and lightwaves cannot?

ty in advance for answering

First off i'am like you I not an expert so dont take this as concrete fact but I would guess its done to the frequencey / wavelength. Its the same for radiation some types can pass through pretty much anything except special shielding and some types can be stoppped by a sheet of paper.

(yes I know that light and radio waves are also types of radiation but i'am using laymans terms!)

Some light can pass through walls though for instance infra red can.Or has tv lied to me again? I remember the scene in robo cop where he sees the guy holding people hostage through a wall.

P.S Welcome to the board!

thank you for your answer and kind welcome. i know radiowaves have a a bigger wavelength than lightwaves but could someone please be more specific as to the exact workings. why does larger wavelength mean it can go through a wall?

I can not answer your question, but I can observe that since I have aluminum siding on my house, radio and TV waves have a difficult time coming through that metal. I have to run a radio antenna outside the house so I can get a better short-wave signal, and I have to do that with my TV antenna too.

I’ve heard that a satellite dish won’t work if you put it in an attic that has a metal roof on the house. Also, when it rains on my outside satellite dish, my TV picture breaks up and sometimes goes out completely.

I have a radio-transmitter outdoor thermometer, and I have to keep it near a window so the radio signals can come into my house. It has trouble transmitting through the aluminum siding.

Because the material in the walls doesn't readily absorb the radio waves. (This isn't meant to be smart-alecky, even if it sounds that way.)

All materials absorb radiation at frequencies determined by the electronic structure of their constituent molecules. We use glass as windows because it doesn't redily absorb photons in the visible range, but we choose the material for wall based on other criteria (e.g. looks, availability and structural properties. And we don't actually want light to go through!)

Metals tend to be really good at absorbing radiation in that range, as are (generally) any materials that have a large number of states for electron excitation.

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Do atomic clocks have to be insulated and shielded to keep out unwanted EM waves? If so, if they were not shielded, would some EM waves alter the “tick rates” of the clocks?

OK, so radio waves (fotons) just go through the empty space of most bodies, sometimes bouncing against electrons, but not having enough energy to really move these electrons up to another level? In other words, they do not get absorbed because the energy cannot be USED in any way, something like that?

But I don't understand, because the fotons will at least move the electrons to which they bounce and loose their energy that way? While light fotons, which have more energy, will likely have a bigger chance to survive all the bouncings and have enough energy left to cross the entire body?

Well, obviously I don't understand this at all.

The fact is that I don't understand at all what a WAVE is. Yes, it's some sort of electronic or magnetic FIELD, in which a particle (foton) moves, but this foton moves in a straight line.

Now I know that we must regard light as sometimes being a wave and sometimes a particle, but what is JUST a wave? What is waving then?

BTW, I know this other guy, Bernard, we were chatting about this earlier.

Basically that. A photon is only useful if it has the exact energy needed to move the atom to an excited state (possibly the infinitieth excited state which involves ionisation). If no transition is requires the energy of incident photons, then it will pass through with little incident.

That's the classical idea. But the quantum idea is all about packets of energy. If a transition between energy states requires 100eV, the classical idea is that if a wave containing 150eV comes along, it will do the excitation thang and carry on with 50eV left. But according to quantum theory, which is more accurate at this level, a 150eV photon will not have any effect because it doesn't have the exact energy level required.

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I believe the way to interpret it is that a large number of photons travelling together will approximate to a wave like thing.

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If I understand the situation correctly, there are two different theories about “what is waving”. I think the most common theory is that it is the electric and magnetic fields that are “waving”, and they zip through space at 186,000 mps as they “wave”. In other words, a light bulb and a radio transmitter generate these tiny little alternating electric and magnetic fields, and they "wave" or "wiggle" as they travel through space.

The other theory is the minority opinion, and it says that what “waves” are the electric and magnetic fields that are already everywhere in space, and that all a light bulb and a radio transmitter does is start the local electric and magnetic fields to “waving” at the light bulb and the transmitter, and it is the “wave”, not the fields, that go zipping through space. This is a type of “ether” theory, so it is not very popular among physicists, although they will often talk about the “waves”, rather than the “fields”, traveling through space.

The way I understand it is that a bunch of little waves traveling together in a “wave packet” group, constitutes a single “photon”. And so, several different groups of little “wave packets” constitute several “photons”, with one group out front and the others following that one. I don’t know if this is correct, but this is the way I imagine what the physicists are saying.

With this idea, a large number of photons traveling one after another, constitute a light “ray” or “beam”. While a lot of them traveling side by side, constitute a wide light “wavefront”. If a large number travel side by side, and more are following behind those, then we have a wider “beam” or “ray” of light.

It is the individual “wave trains” of several photons traveling in a straight line, one behind the other, that constitutes a very narrow “beam”. And when a light bulb generates a lot of photons in all directions, then a lot of individual “beams” diverge and go out in an expanding “spherical” manner, and this is what the “inverse square law” describes, that is, the gradual divergence of all these individual narrow photon “beams”.

In other words, the individual “beams” of single photon “wave trains” get further and further apart, the further they move away from a light bulb. Because of this phenomenon, a flashlight has a curved mirror behind the bulb, which changes the direction of some of these photon “beams” and focuses them to all go out together in a fairly straight line in the direction in front of the flashlight bulb.

A single photon:

~

A single photon “beam”:

~~~~~~~~~~~~

Several photon beams coming out of a flashlight as a “light ray”:

~~~~~~~~~~~~~
~~~~~~~~~~~~~
~~~~~~~~~~~~~

Glom, that makes sense! It's the 'quantum amount' that will determine if there is no interaction at all, in an energy-kind of way.

Sam, I still don't understand, because an electric field is only measurable (or maybe even existing) when MATTER is involved, so a particle must be IN this field. or doesn't it (in light theory)? I mean, when they say that light can EITHER be regarded as wave OR as particle, how can it be ONLY a wave? Or is that not what they mean then?

Sam, that also was what I was thinking: I guess it cannot be that 1 photon is really 'something', or a particle, because they say that a radio photon has less energy (longer wave) than a light photon, but all photons have no mass (or not detectable) and all photons travel at the same speed (speed of light), so one photon cannot have more or less energy than another.

But the shorter the wave, the more photons will be fired in 1 time frame, so we can say: the number of photons in 1 time frame is the energy of the 'photon'.

What you are missing here Sandor is that photons have momentum which, because a photon has no rest mass, is the photons energy. A photon of visible light wave has more momentum than a photon of a radio wave.

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Tensor, but momentum is mass x velocity. Velocity is always the same and there is no real mass, or what? Mass is increasing when velocity increases, but velocity of all photons is the same and there is no mass? I don't understand.

You are using the Classical (Newtonian) formula. In Relativity, momentum for massless particles is defined as p = E/c Where p is the momentum, E is the total energy, and c is the speed of light.

Under relativity, the total energy of a system increases (not mass) as velocity increases, but the total energy also includes momentum as well as mass. In the case of photons, because they have no rest-mass, the total energy of a photon is equal to its momentum.

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OK, but can you explain why a light photon has more momentum than a radio photon? The electrical/magnetic wave 'around it' is shorter, so there are more waves in 1 space frame, but is this wave actually 'pulling it' forwards? Photons have no electrical charge I believe... (I'm just guessing around)

I read that it is impossible for an object with any mass to travel at the speed of light, because when it comes closer to c, mass will increase, and it will increase so much that you will need all the energy in universe and more to get it at c. I understand what you're saying about ENERGY increasing and not mass, but the explanation above doesn't make sense then.

Hello:
An analogy for an electromagnetic wave is an audio wave-the peaks and the troughs represent amplitude, the number of frequencies represents pitch. The difference though is that lower frequency wave can past through walls much easier than higher freqs, it's just the opposite with electromagnetic waves.