# How the energy of light changes

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So doesn't that mean I interact with all of the photon regardless of how far away I am from the actual end of the photon if I only touch the first part of it? But then how could that doppler effect work?

I don't see what the problem is with the Doppler effect. If there is relative motion the frequency changes. The problem seems to be with your model of how this all works. Photons do not act like marbles or drops of water.

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That is why there is this thing called the wave-particle duality for the photon. Your question is easily answered when you consider the wave aspect of the photon and ignore the particle-uncertainty principle.

The Heisenberg Uncertainty Principle is only significant at very small measurements and radio waves are not small.

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I don't see what the problem is with the Doppler effect. If there is relative motion the frequency changes. The problem seems to be with your model of how this all works. Photons do not act like marbles or drops of water.

My problem is your saying that by only touching the first part of the photon, that I am somehow perceiving all of it, which can't be true because if I red-shift a photon, then that means less of the photon is hitting me per second, or in other words, less of the wave-crests are hitting me per second.

That is why there is this thing called the wave-particle duality for the photon. Your question is easily answered when you consider the wave aspect of the photon and ignore the particle-uncertainty principle.

The Heisenberg Uncertainty Principle is only significant at very small measurements and radio waves are not small.

But the reason radio waves are so large is because of he uncertainty principal. Something with such low relative mass is that much more delocalized.

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Actually radio waves (should mean its wavelengths) are large because its frequency is low and that makes its wavelength large (i.e. their product (frequency x wavelength) gives the speed of propagation of the radio wave)

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My problem is your saying that by only touching the first part of the photon, that I am somehow perceiving all of it, which can't be true because if I red-shift a photon, then that means less of the photon is hitting me per second, or in other words, less of the wave-crests are hitting me per second.

And I'm saying that your model is flawed. You can't "touch part of a photon" If you measure its properties, you will have interacted with the whole thing.

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Questionposter: think of the photon as a wave, then think of a seismic wave. You can't "touch" a seismic wave, but you can feel it. That means you're interacting with it. But a seismic wave isn't some "whole thing" like a billiard ball, it's just a wave. You can interact with it briefly before I pull you up on a rope and get you back into the helicopter. Or you might have placed a little accelerometer on the ground. It has scant effect on the seismic wave. When it comes to photons there's something called "weak measurement" that's a bit like this. See The secret lives of photons revealed, a physicsworld article.

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Questionposter: think of the photon as a wave, then think of a seismic wave. You can't "touch" a seismic wave, but you can feel it. That means you're interacting with it. But a seismic wave isn't some "whole thing" like a billiard ball, it's just a wave. You can interact with it briefly before I pull you up on a rope and get you back into the helicopter. Or you might have placed a little accelerometer on the ground. It has scant effect on the seismic wave. When it comes to photons there's something called "weak measurement" that's a bit like this. See The secret lives of photons revealed, a physicsworld article.

I can touch a wave if want just by putting my hand in the water. In fact touching a wave is how you can interact with photons at all since they are part wave. When you touch the wave of a photon, it bumps an electron to a higher energy level. If it was just "feeling" a wave, then the photon would leave on its own without an electron going to a previous energy level due to the fact that as a wave a photon is still traveling, although I still don't get that swan, how does the energy of the entire wave instantaneously transport to one single interaction point? Because photons occupy at least 3 dimensions right? They move in at least a 3 dimensional way which is why they can stretch to be as big as football fields. So if a photon has a length of a football field, how does the energy contained in the part of the photon that's in the back suddenly become tranported to the front where it was touched?

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if a photon has a length of a football field, how does the energy contained in the part of the photon that's in the back suddenly become tranported to the front where it was touched?

It doesn't. But them, it's not going to kick an electron up a quantum level that's very big. The energy of a 100m wavelength photon is about 10 neV (nano electron-Volts). To interact with only "part of the photon" interaction time would have to be less than a microsecond. It's not going to be that short.

It's like saying you are going to jump in front of a bus and touch the front, and then jump back out of the way, so you only get a small part of the energy of the bus. But you cannot possibly react that fast, so the notion is flawed. Atomic response times scale with the energy difference (for dipole interactions, it's the cube of the energy), i.e. lower-energy transitions take longer to occur. Much longer than it takes for the photon to "pass by". You can't interact with only part of a photon. Your model of how this happens is WRONG. You have to discard it.

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I can touch a wave if want just by putting my hand in the water.
You're actually touching the water rather than the wave. That might sound like splitting hairs, but the distinction is important. You aren't touching a seismic wave if you touch the ground. You're touching the ground. The ground is shaking. You can feel it shaking, but you aren't touching "the shaking", which is what the wave is.

In fact touching a wave is how you can interact with photons at all since they are part wave. When you touch the wave of a photon, it bumps an electron to a higher energy level.
Not necessarily. Take a look at refraction.

...how does the energy of the entire wave instantaneously transport to one single interaction point?
Who says there's a single interaction point? Electrons have a wave nature too. See for example hyperphysics and electron diffraction.
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This thread has brought up an enigma for me. If photons are easily "visualisable" for very short wavelength rays like gamma and x-rays as packets of EM energy, how about radio waves whose wavelengths stretch for kilometers? How does it *fit* into a photon?

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All fundamental particles (photons, electrons, , etc.) travel like a wave and "hit" like a particle. Photons at all frequencies, whether visible light or radio frequency or any other, work this way.

Consider the double-slit experiment. Turn the light source way down so that it sends out only one photon at a time. The photon travels like a wave, goes through both slits, but is detected on the screen in only one location. Repeat the experiment with another photon, and it hits at a different location. (There is no way to predict where each photon will be detected, only the probability it will be detected at a certain location). Over time, the photon detector pattern builds up and shows interference (there are places where the photons do not show up).

This same kind of interference pattern shows up for electrons in the double-slit experiment. This says that electrons too travel like a wave and hit like a particle.

So are photons, electrons, etc. particles or waves? As Richard Feynman said, they are neither. They are their own quantum mechanical thingies. There is no word in English (or any other human language as far as I know) which fits the description of how subatomic particles behave.

Edited by IM Egdall
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It doesn't. But them, it's not going to kick an electron up a quantum level that's very big. The energy of a 100m wavelength photon is about 10 neV (nano electron-Volts). To interact with only "part of the photon" interaction time would have to be less than a microsecond. It's not going to be that short.

It's like saying you are going to jump in front of a bus and touch the front, and then jump back out of the way, so you only get a small part of the energy of the bus. But you cannot possibly react that fast, so the notion is flawed. Atomic response times scale with the energy difference (for dipole interactions, it's the cube of the energy), i.e. lower-energy transitions take longer to occur. Much longer than it takes for the photon to "pass by". You can't interact with only part of a photon. Your model of how this happens is WRONG. You have to discard it.

But if my model is wrong, that's saying photons don't take up 3 dimensional space. But then you also say that something like a radio photon takes longer to interact with an electron, so doesn't that mean that a photon 3 dimensional has to completely run into an electron in order to absorbs itself completely an electron up to the next energy level? And if it doesn't, then its still the same problem because that means that an electron can still only interact with part of a photon. How does something oscillate at the wavelength of a football field and bend around objects and not exist in at least 3 dimensions?

Also, how are such low energy level photons created if electrons can't absorb them?

Also, I CAN jump in front of a bus and back out of the way if its traveling slow enough, and even if it was moving fast, so what? It's still possible at a highers speed. Maybe i should make GIFs in photoshop to show you the visual problems.

Edited by questionposter
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But if my model is wrong, that's saying photons don't take up 3 dimensional space. But then you also say that something like a radio photon takes longer to interact with an electron, so doesn't that mean that a photon 3 dimensional has to completely run into an electron in order to absorbs itself completely an electron up to the next energy level? And if it doesn't, then its still the same problem because that means that an electron can still only interact with part of a photon. How does something oscillate at the wavelength of a football field and bend around objects and not exist in at least 3 dimensions?

Also, how are such low energy level photons created if electrons can't absorb them?

Also, I CAN jump in front of a bus and back out of the way if its traveling slow enough, and even if it was moving fast, so what? It's still possible at a highers speed. Maybe i should make GIFs in photoshop to show you the visual problems.

Yes, the whole photon has to interact. This takes time — it's short, but not instantaneous.

here's an example: Rb's first excited state has a lifetime of about 25 ns. If you tried to drive excitation and stimulated emission, it would cycle with a period of no shorter than 50 ns. It simply will not respond any faster than that. The wavelength is of order a micron. In 25 ns, a photon travels around 8m.

Interacting with the "front of the photon" simply has no meaning. It's a flawed model of how things happen.

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And I'm saying that your model is flawed. You can't "touch part of a photon" If you measure its properties, you will have interacted with the whole thing.

Well what about radio waves traveling through solid buildings and hitting other cellphone antennae? When someone calls me, the radio signal isn't just directly transported to my cellphone, it travels through thousands of different things including other objects that will pick it up. They measure the radio photon way before it reaches me, yet I still receive the signal as if it hasn't been determined to a single point already.

Are you trying to say a photon doesn't actually occupy at least 3 dimensions?

Edited by questionposter
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Are you trying to say a photon doesn't actually occupy at least 3 dimensions?

No.

Well what about radio waves traveling through solid buildings and hitting other cellphone antennae? When someone calls me, the radio signal isn't just directly transported to my cellphone, it travels through thousands of different things including other objects that will pick it up. They measure the radio photon way before it reaches me, yet I still receive the signal as if it hasn't been determined to a single point already.

If a photon makes it to you, it was not "measured" by anyone else.

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No.

If a photon makes it to you, it was not "measured" by anyone else.

So when an interaction occurs with a photon, all of the photon instantaneously transports to the point where it measured, that's what your saying. If photons occupy 3 dimensions, then in order to only perceive photons at a 1 dimensional sphere (or point) there has to be some kind of instantaneous transport and/or destruction of the rest of the photon which was 3-dimensional units away from the point where the first part of the photon was measured.

Edited by questionposter
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So when an interaction occurs with a photon, all of the photon instantaneously transports to the point where it measured, that's what your saying.

No, I've said the interaction is NOT instantaneous more than once.

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No, I've said the interaction is NOT instantaneous more than once.

But then how can

Interacting with the "front of the photon" simply has no meaning.

be true? If a photon takes time, then doesn't that have to mean that only part of it can touch something before all of it reaches something since it travels at a specific speed?

Edited by questionposter
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So if there's a nuclear bomb, then to not die from the radiation, all I have to do is travel at nearly the speed of light away from the blast site just before it hits me and the gamma rays which are gamma rays to many other people will suddenly turn into radio waves which won't effect me at all and travel harmlessly through me since their wavelength will somehow be stretched out just because I'm moving away which the photon can't even know because they havn't hit me yet?

Or are you trying to say what's measured isn't actually what a physical object is?

That will work. But the acceleration necessary to reach relativistic speed relative to the location of the detonation of the bomb in time to be effective will plrobably kill you.

But then how can

be true? If a photon takes time, then doesn't that have to mean that only part of it can touch something before all of it reaches something since it travels at a specific speed?

A single photon is a point particle. It has neither a front nor a back.

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But then how can

be true? If a photon takes time, then doesn't that have to mean that only part of it can touch something before all of it reaches something since it travels at a specific speed?

The Heisenberg Uncertainty Principle renders this model meaningless.

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The Heisenberg Uncertainty Principle renders this model meaningless.

How? In the uncertainty principal things still have a specific 3 dimensional space which they can occupy based on specific mass or energy. A particle of light has a specific energy, so doesn't that mean it has a specific size? In fact, I'm pretty sure that the more energetic a particle is the less localized it is because of the uncertainty principal in the first place.

Also, what "model"? I only said a photon occupies 3 dimensions, which you agreed with, and therefore because it occupies 3 dimensions and only travels at a specific speed, only one part of the 3 dimensional photon can touch something at any given time, just like only part of a bullet makes contact with a wall at first even though a bullet is traveling really fast.

Are you trying to say that "part" of a photon doesn't interact with things? Because that's different than saying that a part of a photon doesn't "touch" something else. A low energy radio photon "touches" other objects, but it doesn't interact with them.

That also reminds me that you said a radio wave can only reach and interact with your phone by only interacting with your cellphone and no others, but then how can other people listen in an a conversation your having?

Edited by questionposter
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How? In the uncertainty principal things still have a specific 3 dimensional space which they can occupy based on specific mass or energy. A particle of light has a specific energy, so doesn't that mean it has a specific size? In fact, I'm pretty sure that the more energetic a particle is the less localized it is because of the uncertainty principal in the first place.

Also, what "model"? I only said a photon occupies 3 dimensions, which you agreed with, and therefore because it occupies 3 dimensions and only travels at a specific speed, only one part of the 3 dimensional photon can touch something at any given time, just like only part of a bullet makes contact with a wall at first even though a bullet is traveling really fast.

You can't determine what is happening in times below what the HUP dictates. You're treating a photon like a classical object, and it's not. A photon is not a bullet.

Are you trying to say that "part" of a photon doesn't interact with things? Because that's different than saying that a part of a photon doesn't "touch" something else. A low energy radio photon "touches" other objects, but it doesn't interact with them.

That also reminds me that you said a radio wave can only reach and interact with your phone by only interacting with your cellphone and no others, but then how can other people listen in an a conversation your having?

No, I said a photon that makes it to you didn't interact. A radio wave sent to/by a phone consists of many photons. A 1 W source of 1 GHz radiation is emitting 1.5 x 10^24 photons a second.

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You can't determine what is happening in times below what the HUP dictates.

I'm having understanding what your trying to say here. So.. the uncertainty principal says you can't base future information off of past information too right? Are you trying to say that "part" of a photon can't interact with a particle because then that would be assuming that you can base the location of the rest of the photon based on where the first part hit in the past? But a photon doesn't have a finite position so I couldn't anyway, and neither does an electron so there doesn't have to be past or present information, it's just all one single photon which is in of itself a wave which occupies a (sometimes) large 3 dimensional area. Wouldn't it be more like waves hitting in the water? Only part of the waves can meet.

Edited by questionposter
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$\Delta{E}\Delta{t}>\hbar$

If you change the energy of the atom, you can't determine what is happening in short time frames. Like in the Rb example I gave earlier. You can't determine the state of the atom any faster than ~25 ns. Talking about what's going on at any shorter time scales is nonsensical.

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$\Delta{E}\Delta{t}>\hbar$

If you change the energy of the atom, you can't determine what is happening in short time frames. Like in the Rb example I gave earlier. You can't determine the state of the atom any faster than ~25 ns. Talking about what's going on at any shorter time scales is nonsensical.

Maybe all of the photon needs to pass into the electron to get absorbed, or maybe the photon changes to a different photon as the first part get's absorbed, which means that the thing you were saying would't apply because it's not the same photon once the first part get's absorb. If one wavelength of a 300 nano-meter photon suddenly disappears, is it a 299 meter wavelength or does it stretch out more to become a 301 nn wavelength? A photon has to travel only specific distance in time since it's speed isn't instantaneous, so there's obviously something going, but because of that HUP thing you just said, we know that energy can't be continuously absorbed from a single photon, so I think one of the two things I was saying is true or near-true, although how does a photon that's bigger than the cloud of an electron fit entirely inside an electron without part of it already passing through the other side by the time the end of the photon reaches it?

Edited by questionposter

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