Argument Question

Drifter said:
I'm not sure how "more photons" would not change frequency. If light is a stream of photons then increasing the number of photons over a given period of time would increase the frequency of photons striking or passing an object, wouldn't it? What else could frequency mean if we are talking about particles instead of waves?
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Thinking of light as particles, the "frequency" is the energy content of each individual photon. If you think of them like projectiles, it's the same as increasing the mass of each projectile. Since you mentioned thinking of physical entities mainly as waves rather than particles, you've probably heard of the de Broglie relations which can express the energy of (all) particles in terms of frequency.

In general photons do not arrive in regularly-spaced intervals, and this is not what defines the frequency of light. If you'd like to prove it to yourself, shine two laser pointers of the same color at the same spot, and note that the point of light created is still the same color (the frequency hasn't changed) even though the number of photons arriving per second should now be doubled. Instead, the spot is just brighter than if only one laser were used.
 
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Sapphyre said:
Thinking of light as particles, the "frequency" is the energy content of each individual photon. If you think of them like projectiles, it's the same as increasing the mass of each projectile. Since you mentioned thinking of physical entities mainly as waves rather than particles, you've probably heard of the de Broglie relations which can express the energy of (all) particles in terms of frequency.
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This is compatible with what I've read: the energy of a photon is inversely proportional to the wave length (which determines frequency). In other words, it is a wave function. Increasing the energy apparently increases the frequency. This doesn't seem to jibe with what you said earlier:" If we think of light as particles, then it [increasing intensity] means "more photons". Either way, it's making the light brighter without changing the frequency."

I don't understand what you mean by "intensity" if it is somehow different from "energy".
In general photons do not arrive in regularly-spaced intervals, and this is not what defines the frequency of light. If you'd like to prove it to yourself, shine two laser pointers of the same color at the same spot, and note that the point of light created is still the same color (the frequency hasn't changed) even though the number of photons arriving per second should now be doubled. Instead, the spot is just brighter than if only one laser were used.
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True. But this result is what would be expected of light waves.

Light waves are generally depicted as sine waves, giving the impression of regularly spaced intervals at a given frequency. I don't understand the concept of randomly spaced photons within this framework. I can understand how it might appear a photon could be present at a random point within a wave form, but this could be due to the random point of detection that caused the collapse of the wave. (I'm using the term "understand" loosely. I'm in over my head. :))

What makes you so sure that there is a fundamental building block to begin with?
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I'm not sure of anything. I'm beginning to wonder if "quantum", itself, isn't a good description of a potential candidate for "fundamental building block"; Discrete quantities of something that, at various times, we call mass, energy, particles, or waves, depending on how we look at them.
 
Talking of quantum uncertainty and the weirdness of photons, I love the experiment you can do with three polarising filters.

A polarising filters allow only certain light photons having a particular "alignment" to pass through. Look through a polarised lens and everything will look dimmer -- like looking through sunglasses.

If you look through two polarising lenses that are in perfect alignment, it will look the same as looking through one lens. But, as you rotate one lens 90 degrees, less-and-less light comes through until the pair of lenses appear opaque black.

Place a third lens on top. Even though (last time you checked) there was almost no light coming through the first two lenses... you can rotate the third lens to allow more light through... Almost as if the final lens is adding back photons that were filtered out by earlier lenses!

Of course that's not what's actually happening... But scientists are, for once, completely unified in agreement that this is pure magic.

[video=youtube;zcqZHYo7ONs]https://www.youtube.com/watch?v=zcqZHYo7ONs[/video]

Oh -- and magnets. They're pretty subatomically awesome too. Am I the only one who feels a tingle of scientific amazement every time they use a fridge magnet...? :eek:

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Drifter said:
I'm in over my head. :)
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Ditto!

Drifter said:
Light waves are generally depicted as sine waves, giving the impression of regularly spaced intervals at a given frequency. I don't understand the concept of randomly spaced photons within this framework. I can understand how it might appear a photon could be present at a random point within a wave form, but this could be due to the random point of detection that caused the collapse of the wave. (I'm using the term "understand" loosely. I'm in over my head. :))
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The way I'm reading your interpretation, I think you're making a mistake.

It sounds like you're seeing photon particles as being the physical medium through which wave energy is transmitted -- a bit like air particles and sound waves.

But light is different -- it's an electromagnetic wave that can travel in a vacuum with no particles. It behaves as a particle-less wave UNTIL it's probability state collapses to form photons.

In other words, the "frequency" refers to the wave frequency; not the frequency of the photon particles themselves.
 
This is still going? What have I done......

Seriously thought some good reading here.
 
Drifter said:
This is compatible with what I've read: the energy of a photon is inversely proportional to the wave length (which determines frequency). In other words, it is a wave function. Increasing the energy apparently increases the frequency. This doesn't seem to jibe with what you said earlier:" If we think of light as particles, then it [increasing intensity] means "more photons". Either way, it's making the light brighter without changing the frequency."

I don't understand what you mean by "intensity" if it is somehow different from "energy".
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Basically, you have two parameters that both factor into the energy content of a beam of light (through a fixed surface area). One is the frequency (let's assume the light is monochrome for simplicity), and the other is the intensity. If you think of light as waves traveling at c, you could increase their energy by either increasing their frequency (making the wavelength shorter) or their amplitude (making the waves taller …or, equivalently, just adding more waves since they can combine). Alternatively, if you think of light as particles, you could increase the energy of the particle stream by either making each particle more energetic (increasing its de Broglie frequency) or by having more particles striking per unit time (greater intensity). You can increase the energy from a laser light by either blue-shifting the color while keeping the same brightness, or by increasing the brightness while keeping the same color.

In Physics, intensity is distinct from energy per se, but related: Intensity (physics)
 
Fascinating video, tiny!
tiny said:
Place a third lens on top. Even though (last time you checked) there was almost no light coming through the first two lenses... you can rotate the third lens to allow more light through... Almost as if the final lens is adding back photons that were filtered out by earlier lenses!

Of course that's not what's actually happening...
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That additional light is coming from somewhere, and it is consistently observed with the addition of a 3rd lens in the right orientation. Actually, with my limited grasp of what scientists have been say about particle physics, I don't have a problem with the idea that the 3rd lens somehow 'added' 'photons'.

What I believe is happening is consistent with my reading of experimental results and the concept of conservation of mass/energy. No matter whether light takes the form of a wave, particle, both, or neither, the energy in light doesn't vanish from the universe after interacting (colliding) with some other wave/particle. The original wave/particle will collapse and/or be 'destroyed', but the energy will be instantly transformed into one or more waves/particles, sometimes the same kind as the original. Everything I think I know about particle accelerator experiments tells me that there is a whole lot more subatomic activity going on among those lenses than just photons shooting through like little bullets. Two polarized lenses in the right orientation may stop visible light, but they obviously don't stop the flow of energy capable of creating a particle circus.
The way I'm reading your interpretation, I think you're making a mistake.
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What??? Impossible!!! :laugh:
It sounds like you're seeing photon particles as being the physical medium through which wave energy is transmitted -- a bit like air particles and sound waves.
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I don't actually see it that way. I see "photon" as one of the ways to measure light and/or describe it's apparent behavior in certain situations. This would apply to "wave", too.

As for "medium", we can give that medium a name: "field", like they do in that video when they say photons are waves in the electromagnetic field. But that doesn't tell us anything about it's physical properties, or if it even exists. It just gives us an easy way to talk about things we don't understand.

In that video they depict photons as discrete, seemingly independent packets of waves, like a blend of particles and waves. I'm not ready to buy that yet. Seems like a cop-out answer to the wave/particle question. But that's just me.
Oh -- and magnets. They're pretty subatomically awesome too. Am I the only one who feels a tingle of scientific amazement every time they use a fridge magnet...?
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You are not alone.

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Sapphyre said:
In Physics, intensity is distinct from energy per se, but related: Intensity (physics)
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Thanks for clearing that up. It's still unclear how "intensity" would apply to settling wave/particle duality issues. I'll have to work on that.
 
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