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11-23-2011, 03:06 PM #49
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by honeyx The blue one is burning much much better. Itīs the dual nature of the photons acting like energy but also like material.
It's absorption, not energy per photon. Again, by your logic, microwave ovens aren't possible because the energy per photon is so low

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11-23-2011, 03:18 PM #50
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Re: Prove my science teacher wrong!

If your blue burns better, it must be because better focus or different absorbtion of the material.
Iron will do more damage, because it's will have larger energy density at impact (if I ignore air resistance). Ie. it's the same as focus of the laser. But we are talking about lasers with SAME power/energy density.
Photons can be reflected, and add no energy to the material, or they can be absorbed, in which case all of their energy will be converted to heat. There is just energy in photons, no mass. There is also only complete reflection or complete absorbtion of individual photons.
If we talk about material which absorbs both wavelengths in same amount (ie same percentage of photons absorbed/reflected), we also talk about same amount of heat added to the same area. There simply is no difference.
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11-23-2011, 04:56 PM #51
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by Cyparagon It's absorption, not energy per photon. Again, by your logic, microwave ovens aren't possible because the energy per photon is so low
Sure ítīs absorbtion too, but your analogy with an microwave oven isnīt quite accurate. Of course microwaves do have a lower energy level, but the amount of photons emmited by a microwave oven against a 1W laser is huge. How much Watts does such a oven have? So you are comparing a small river of lava with flooding a complete country with water?

Quote:
 Originally Posted by DrSid If your blue burns better, it must be because better focus or different absorbtion of the material.
I was refering to black materials that absorb them the same and the lasers to be focused to the same size.

Quote:
 Originally Posted by DrSid Iron will do more damage, because it's will have larger energy density at impact (if I ignore air resistance).
Yes, there you are right. But why? Because the single atoms do have a larger energy density. Like single blue photons.

Quote:
 Originally Posted by DrSid Ie. it's the same as focus of the laser. But we are talking about lasers with SAME power/energy density.
In this case you also are right. Itīs just the single photons do have a higher energy density.

You can compare this with a small atombomb vs a bomb with the same weight with normal explosives and every photon being such a bomb. Even just a few of them will cause more demage than a ton of the normal bombs.

Quote:
 Originally Posted by DrSid Photons can be reflected, and add no energy to the material, or they can be absorbed, in which case all of their energy will be converted to heat.
Thatīs why i said it has to be compared under the same conditions.

Quote:
 Originally Posted by DrSid There is just energy in photons, no mass.
Sorry, but there you are wrong and should do some reading about the dual nature of photons also acting like having mass. Sure they have no mass, but hitting mass they are acting like having one. So just saying photons do not have a mass is the half truth.

Quote:
 Originally Posted by DrSid There is also only complete reflection or complete absorbtion of individual photons. If we talk about material which absorbs both wavelengths in same amount (ie same percentage of photons absorbed/reflected), we also talk about same amount of heat added to the same area. There simply is no difference.
Ok. I will tell you a simple experiment you can do yourself. Take a 1W blue laser and shine it unfocused on your arm. Then take a 1W IR laser and do the same, but focused to a pinpoint. I assure you, your skin will absorb the IR better, but you will feel the difference.

Last edited by honeyx; 11-23-2011 at 05:02 PM.

11-23-2011, 05:33 PM #52
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Re: Prove my science teacher wrong!

Photons are massless, and their momentum is directly proportional to their energy. Therefore your concept of a "heavier" photon having more momentum is meaningless.

1 photon with an energy of 1eV will have exactly the same energy AND exactly the same total momentum as 2 photons each with an energy of .5eV (provided they're traveling in the same direction, of course).

A 1W beam of red photons carries exactly the same amount of energy as a 1W beam of blue photons, AND both carry exactly the same amount of momentum as well, because photon momentum is directly proportional to photon energy.

Last edited by pullbangdead; 11-23-2011 at 05:44 PM.

11-23-2011, 06:05 PM #53
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by honeyx Sure ítīs absorbtion too, but your analogy with an microwave oven isnīt quite accurate. Of course microwaves do have a lower energy level, but the amount of photons emmited by a microwave oven against a 1W laser is huge.
How about this then: are you claiming 1W 10600nm will be vastly inferior to 1W of blue at burning things?
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11-23-2011, 06:28 PM #54
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by pullbangdead Photons are massless, and their momentum is directly proportional to their energy. Therefore your concept of a "heavier" photon having more momentum is meaningless. 1 photon with an energy of 1eV will have exactly the same energy AND exactly the same total momentum as 2 photons each with an energy of .5eV (provided they're traveling in the same direction, of course). A 1W beam of red photons carries exactly the same amount of energy as a 1W beam of blue photons, AND both carry exactly the same amount of momentum as well, because photon momentum is directly proportional to photon energy.
Ok so itīs called momentum in english what I tried to describe with being heavier. Thanks for clearing me up about this.

I do not disagree with you on what you said. Itīs all correct. All i wanted to point out is that a photon with an energy of 1eV will cause more demage to the tiny area of mass it is hitting than a few photons with a way lower energy but all together the same amount of momentum hitting the same area.

It will be still a difference a huge meteor with itīs momentum hits a area or a few smaller meteors with all together the same momentum will hit the same area.

Else even a 5mW laser would burn holes into CD cases. You just would have to leave it long enough till the amount of energy and so the amount of momentum a burning laser is having is reached.

Quote:
 Originally Posted by Cyparagon How about this then: are you claiming 1W 10600nm will be vastly inferior to 1W of blue at burning things?
No, Iīm not claiming it will be vastly inferior, but it would make a difference.

For me itīs simpy not the same and you canīt compare it one to one because they all are different weavelenghts and acting different. Therefore I also wouldnīt compare 1W of x-rays to 1W of radiowaves.

And yes. photons are massless, but are acting like having a mass hitting a mass. Be it called momentum. But the shorter the weavelenght, the higher the energy level and so the higher the momentum. But acting like a mass the more energy they a carring the more they are acting like having a bigger mass with itīs bigger momentum.

Last edited by honeyx; 11-23-2011 at 06:48 PM.

11-23-2011, 07:09 PM #55
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by honeyx you canīt compare it one to one because they all are different weavelenghts and acting different.
You mean like you did here?:

Quote:
 Originally Posted by honeyx The blue one is burning much much better. Itīs the dual nature of the photons acting like energy but also like material.
How exactly are they acting different?
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Last edited by Cyparagon; 11-23-2011 at 07:10 PM.

11-23-2011, 07:55 PM #56
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Re: Prove my science teacher wrong!

You got me here But still. You canīt exactly compare them one to one. I did of course some burning tests with both to see how well they are performing. Just of pure curiosity.

Tried a few different kind of black plastics making sure they are also black in the IR specturm and so absorbing IR as well as blue. (Yes, some black plasitcs appear to be black in the visible specturm but to be white in the IR specturm because they are reflecting IR.)

The blue laser had no problem to burn holes through them, even if focused to infinity. The IR laser wasnīt perfoming that well. It took more time to burn holes, just if I focused it to a smaller size than the blue one it burned them as fast as the blue laser.

The blue one can set white paper into flames. The IR laser canīt at all. Even not a colored one. Just a black or quite a black one.

When focused to infinity the blue one at least starts to skoke white paper. Also, the blue laser will stink your skin immediately and it hurts a lot, though a huge amount of it will be reflected. With the IR laser you will feel almost nothing, even if focused to a pinpoint, though most of it will be absorbed by your skin. All you will feel is a pleasant warm feeling where you are pointing it.

And thought the IR is better absorbed by the skin, itīs going deeper into it whereas the blue is just absorbed at its surface.

Thatīs why Iīm saying you canīt compare them one to one. If it comes to burning a blueray is even a much better choice than a 445nm one because of itīs shorter weavelenght, better absorbtion and higher energy level of the photons. But not necessarily because it can be focused better or itīs output power.

Last edited by honeyx; 11-23-2011 at 08:02 PM.

11-23-2011, 08:45 PM #57
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by pullbangdead "Burning ability" is a whole other discussion, and a pretty asinine one in my experience.
I'm just going to leave this one here again....

11-23-2011, 10:17 PM #58
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Re: Prove my science teacher wrong!

"Else even a 5mW laser would burn holes into CD cases. You just would have to leave it long enough till the amount of energy and so the amount of momentum a burning laser is having is reached."

You are assuming that all the properties of heat dissipation are being ignored then aren't you ? Not having the ability to prevent this myself I would think that your example would prove true. If you could keep the applied energy as heat from being lost then, in a perfect example, the point would eventually be reached where the material being exposed would soften and melt, perhaps even "burning" if the exposure was kept up. But of course that can't happen.
I'm finding it difficult to follow your precise thoughts. There seems to be a slight language difficulty. You are trying to explain things beyond your limited vocabulary.
Although far from being a physics major or even having any formal science training I haven't been made aware of photons being proven to have any mass. I am aware of a dual nature as in examples of interference patterns from a single light source showing that light behaves as both particles and waves. But I must have missed something about there being mass involved.
As far as the IR compared to the 445 on your skin : The IR penetrates deeper as you pointed out. This also means that the energy is being spread out. The heat is being absorbed by a much greater area and is also being dissipated by the circulation of your body. (Actually a pretty good biomechanical system for heat transfer.) Then the energy from a 445 is dramatically restricted to a much smaller area that actually is also very poorly set up for removing of the heat. (The top levels of skin are dead and not directly part of the heat transfer system.)
So I would expect the blue to burn you far better than the IR. (Hence the proliferation of IR heaters in industrial buildings and not blue-light heaters.)
I would also question the efficiency of the beams when making a comparison as I believe that IR loses a lot more energy over distance traveled. Is the energy level at the point of exposure actually the same in your tests and examples ? Are you sure that the IR isn't losing a lot more energy to the air and diffusing as it travels ? Perhaps a vacuum chamber test is in order ?
And absorption is a big factor too.
What if you try going the other way with it and make the IR burn much better than the blue ? Pick an item which looks blue and therefore reflects most of the blue light energy directed at it. Trying different shades of blue and different densities (depths of the color layer) while still applying the IR for comparisons would yield much more data of a more scientific nature that the real results could be determined.
Not that I'm saying anyone is wrong.
I am just trying to understand it all.

11-23-2011, 11:11 PM #59
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by honeyx Tried a few different kind of black plastics making sure they are also black in the IR specturm and so absorbing IR as well as blue.
See, that's the point though. It's not. It has a different absorption. If the power is the same and one heats the target more, it can only be because the power of one isn't being transferred as well.

Quote:
 Originally Posted by honeyx ...And thought the IR is better absorbed by the skin...
That's just not true. Skin has much lower absorption in IR. This is exactly why the IR is able to travel further into you - it isn't being absorbed as well.
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11-24-2011, 06:27 PM #60
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by Cyparagon See, that's the point though. It's not. It has a different absorption. If the power is the same and one heats the target more, it can only be because the power of one isn't being transferred as well.
This is just your assumption about having a different absorbtion and the power being not transfered as well, but not a prove. I canīt prove that either because not having the equipment to prove it, so be it like you said. I just said i tried this with different types of black plasitcs, and the results were always the same, which letīs me doubt it always has to ba a different absorbtion and the power not being transfered as well.

Quote:
 Originally Posted by Cyparagon That's just not true. Skin has much lower absorption in IR. This is exactly why the IR is able to travel further into you - it isn't being absorbed as well.
Here you are in general right if just reducing the absorbtion to the upper surface of the skin, but looking at the skin as a whole it has a better absorbtion. And thatīs because less IR is reflected than blue and because itīs going deeper into the skin so to say being better absorbed.

There is simply less reflection and so more energy is going into it, but like ShortyInCanada described it, the heat is better cooled for example by the blood.

I gave this example to show why you canīt compare them one to one. They are simply behaving somewhat different.

Shorty. What Iīm missing here is a lot. For example time. Because time plays a big role too if comparing the energy of different weavelenghts. Thatīs why I gave the example with the 5mW laser. For now I like the word "momentum" (what I called to be the impulse energy) because itīs the energy given by a photon in a specific moment. The sum of two photons with just the half momentum will be the same, but if there is just a small difference in time, it is not given at exactly the same moment. Even then if the distance of the two photons is just a single nanometer and the one of them is hitting the target first.

Reduced just to the sum of the given energy it will appear as the same, but it still will make a difference. This is where we are going into times of pico-, femtosecounds and even smaller time differences.

Btw. Blue is more absorbed over distance than IR. Itīs because itīs more absorbed by the particles in the air.

Also. Photons do of course have no mass, but they are interacting with mass like having one. You can even calculate the theoretical mass of the photons. And this is also why gravity has an influence on the photons and why black holes are sucking all light into them.

The theoretical mass of the photons of course plays also a role in the whole picture and Iīm getting tired of this all if people are just reducing this all to statements like " photons do not have a mass" and "total power is total power" to better argue over their point of view rather than looking at the whole picture.

Oh well. X-rays are something special because they are able to go throught the mass. Itīs because of their high energy level and so also because of their theorietical higher mass. They are the copkiller bullets going through steel like butter.

Iīm aware my limited english skills are a big barrier and am sorry for this.

11-24-2011, 08:46 PM #61
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Re: Prove my science teacher wrong!

You're mixing up ideas, and not all of them are correct as you're applying them.

And as I've already said, the entire argument is very silly anyway.

The original post said "power", and this entire tangent into "burning ability" is pointless.

11-24-2011, 09:13 PM #62
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Re: Prove my science teacher wrong!

Quote:
 Originally Posted by honeyx I just said i tried this with different types of black plasitcs, and the results were always the same, which letīs me doubt it always has to ba a different absorbtion and the power not being transfered as well.
The power being transferred is 100% dependent on absorption.
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11-24-2011, 09:47 PM #63
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Re: Prove my science teacher wrong!

I don't agree with you on that one Pullbangdead...I think this is very enjoyable while I'm sitting here in front of my computer at work looking like I'm doing something.
Also while eating my, so called, lunch.

"theoretical mass" of photons...
effect from black holes...
Hmmmmmm...
Yep. I'm liking this thread !
Stimulating the grey matter...
Always a good thing.

11-25-2011, 03:25 AM #64
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Re: Prove my science teacher wrong!

Cyparagon, you are catching me on words, though you know what is meant by referring to what you said before.

I never said you are wrong. All I want is people are thinking a bit further.

Pullbangdead. I donīt want to be rude. But I donīt think it will be pointless to say you are more than the sum of your atoms and more clever than a stone with the same sum of atoms.

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