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Burning Ability - IR vs Green vs BluRay

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Hi,

From my limited physics knowledge, assuming all 3 lasers are the same output power (say 200mW), it seems to me that an IR laser should be the best among the 3 in terms of the ability to burn stuffs, because IR is directly related with heat radiation. In reality, is this true?

So in real life, what is the order, IR, green and bluray, in terms of the ability to burn stuffs?
 

Things

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Blu-ray should be the best burner, since its as its a shorter wavelength, you can focus it to a smaller dot. Followed by the green, then IR, since IR is wayyy up high in the spectrum.
 

Cyparagon

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Pseudonomen discovered a red beam can actually be focused smaller than a green beam. Why? The initial beam diameter of a red is 4mm. The initial beam diameter of a green is 1mm. Only if one were to expand the green to 4mm (or larger) and then refocus it would one achieve a smaller spot.
 

Things

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I guess that would be true, but I am thinking if everything was perfect I guess :p
 

RA_pierce

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The smallest point you can focus a laser to also depends on the focal length.
A longer focal length (10cm for example) will produce a larger diameter focused beam than if you were to focus it a short distance (1cm).
But because the wavelength of violet light is shorter, the smallest possible diameter of a focused beam from a bluray laser will be shorter than that of a green beam and any other wavelength that is longer than 405nm.

When it comes to burning though, 1mW = 1mW regardless of the wavelength.
The advantage in burning goes to lower wavelength lasers though, because most objects tend to absorb more violet light than IR, red, or green.
For example, a CO2 laser can be used to ablate glass and metals, while a visible laser of the same power may be reflected from the surface or pass through it.
This is because the wavelength of a CO2 laser (deep infrared) is absorbed by these materials better than a visible wavelength.
Another example is the bluray lighting a white match. This short wavelength is absorbed while other wavelengths are reflected.
The other advantage, as already stated, is the ability to focus.

All things being equal, a mW is always equal to a mW.

Heat radiation is not necessarily related to IR light.
The portion of the spectrum of electromagnetic radiation ranges from radio waves (longest wavelength) to gamma rays (shortest wavelength). Infrared is light just as much as green light is light.
Wikipedia says:
"EM radiation has an electric and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy propagation. Electromagnetic radiation is classified into types according to the frequency of the wave, these types include (in order of increasing frequency): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays."

Heat is a different kind of energy. Heat can be transferred through conduction, convection, and radiation (if I remember correctly) and can only be transferred between things that have a difference in temperature. Heat can be measured with a thermometer, lasers cannot.
I don't know exactly how to define heat, but heat is not light, and light is not heat.

Light transfers energy which is absorbed by an object and that energy creates heat... but I can't really articulate what the concept I have in mind.
Someone help me out...
 
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Blu-ray is the best easily-available burner because it is a low wavelength, and is therefore absorbed much better by most colors (such as lighting white matches instantly at 100mW). When it comes to burning versatility, blu-ray is by far the best. However, on a black object, 1mW=1mW.

-Mark
 

Switch

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Heat can be measured with a thermometer, lasers cannot.
No, temperature can be measured with a thermometer. ::) Heat IS energy.
What the op probably meant by "IR is directly related to heat radiation" is this:
Any object that has a temperature (ie above 0 Kelvin) emits radiation called blackbody radiation.This is the radiation that heat can be transfered in.It is indeed part of the EM spectrum, so call it light if you want, but it is actually situated in the IR part of the spectrum in the 8 - 14 um range (that's 8,000 - 14,000 nm) so it's way "deeper" (longer wave) than , say, 808nm or 1064nm which are the most common IR wavelengths that we encounter in our hobby.
Of course , radiation in this range acts in a completely different manner compared to the visible, near UV and near IR spectrum.A CO[sub]2[/sub] laser beam has a wavelength of 10.6 um which is within that range, so it's a good example.
Thermal imaging cameras use a special sensor (a microbolometer) to pick up blackbody radiation, that is basicly emited by everything around us as if it were visible light, and then is converted in the color coded image you see on the screen.

I think when a laser beam hits a surface , what basicly happens is that the photons hit the particles , causing them to move (increasing their energy).As the temperature is given by the movement of particles , more movement = higher temperature.(0K = no movement)
 
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Switch said:
Heat can be measured with a thermometer, lasers cannot.
No, temperature can be measured with a thermometer. ::) Heat IS energy.
What the op probably meant by "IR is directly related to heat radiation" is this:
Any object that has a temperature (ie above 0 Kelvin) emits radiation called blackbody radiation.This is the radiation that heat can be transfered in.It is indeed part of the EM spectrum, so call it light if you want, but it is actually situated in the IR part of the spectrum in the 8 - 14 um range (that's 8,000 - 14,000 nm) so it's way "deeper" (longer wave) than , say, 808nm or 1064nm which are the most common IR wavelengths that we encounter in our hobby.
Of course , radiation in this range acts in a completely different manner compared to the visible, near UV and near IR spectrum.A CO[sub]2[/sub] laser beam has a wavelength of 10.6 um which is within that range, so it's a good example.
Thermal imaging cameras use a special sensor (a microbolometer) to pick up blackbody radiation, that is basicly emited by everything around us as if it were visible light, and then is converted in the color coded image you see on the screen.

I think when a laser beam hits a surface , what basicly happens is that the photons hit the particles , causing them to move (increasing their energy).As the temperature is given by the movement of particles , more movement = higher temperature.(0K = no movement)
Perfectly stated! This is exactly the way it works. Themal energy is really just a form of kinetic energy on a very small scale.

-Mark
 

RA_pierce

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rocketparrotlet said:
[quote author=Switch link=1228291841/0#6 date=1228352373]
Heat can be measured with a thermometer, lasers cannot.
No, temperature can be measured with a thermometer. ::) Heat IS energy.
What the op probably meant by "IR is directly related to heat radiation" is this:
Any object that has a temperature (ie above 0 Kelvin) emits radiation called blackbody radiation.This is the radiation that heat can be transfered in.It is indeed part of the EM spectrum, so call it light if you want, but it is actually situated in the IR part of the spectrum in the 8 - 14 um range (that's 8,000 - 14,000 nm) so it's way "deeper" (longer wave) than , say, 808nm or 1064nm which are the most common IR wavelengths that we encounter in our hobby.
Of course , radiation in this range acts in a completely different manner compared to the visible, near UV and near IR spectrum.A CO[sub]2[/sub] laser beam has a wavelength of 10.6 um which is within that range, so it's a good example.
Thermal imaging cameras use a special sensor (a microbolometer) to pick up blackbody radiation, that is basicly emited by everything around us as if it were visible light, and then is converted in the color coded image you see on the screen.

I think when a laser beam hits a surface , what basicly happens is that the photons hit the particles , causing them to move (increasing their energy).As the temperature is given by the movement of particles , more movement = higher temperature.(0K = no movement)
Perfectly stated!  This is exactly the way it works.  Themal energy is really just a form of kinetic energy on a very small scale.

-Mark[/quote]

That's basically what I wanted to say, thanks for the explanation... :)
However, I never said temperature can't be measured with a thermometer... :-?
But still, "heat" is different than even deep IR.
 

Xplorer877

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rocketparrotlet said:
Blu-ray is the best easily-available burner because it is a low wavelength, and is therefore absorbed much better by most colors (such as lighting white matches instantly at 100mW).  When it comes to burning versatility, blu-ray is by far the best.  However, on a black object, 1mW=1mW.

-Mark
Some black surfaces reflect IR and some types of visibly clear glass absorb IR. In my experiences it is easier to focus 405nm light than any other. Even though 405nm is high energy (blue fire is hotter than yellow fire), 1mW is still 1mW when it comes to heating surfaces with a laser.
 
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Xplorer877 said:
1mW is still 1mW when it comes to heating surfaces with a laser.
Yes, assuming equal absorption by the object. However, this is rarely the case, leading to differences in burning between different wavelengths.

By the way, heat is a measure of energy (e.g. a bathtub full of water at 80 degrees has more heat than a cup of water at 80 degrees), but temperature is a measure of energy/quantity (e.g. the bathtub of water and the cup of water have the same temperature.)

-Mark
 
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rocketparrotlet said:
[quote author=Xplorer877 link=1228291841/0#9 date=1228366625]1mW is still 1mW when it comes to heating surfaces with a laser.
Yes, assuming equal absorption by the object. However, this is rarely the case, leading to differences in burning between different wavelengths.

By the way, heat is a measure of energy (e.g. a bathtub full of water at 80 degrees has more heat than a cup of water at 80 degrees), but temperature is a measure of energy/quantity (e.g. the bathtub of water and the cup of water have the same temperature.)

-Mark
[/quote]
the correct part is that temperature is a measure of heat energy. it's basically a measure of how hot or how cold a matter is, like 30 degrees celsius. now the wrong part is that, heat is already a form of energy, so i don't get why you say that "heat is a measure of energy". also, you can say something "has a higher temperature", but not "more heat". it's wrong isn't it? heat energy can only be measured by temperature, so you should use the word "temperature".
 

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RA_pierce said:
That's basically what I wanted to say, thanks for the explanation... :)
However, I never said temperature can't be measured with a thermometer...  :-?
But still, "heat" is different than even deep IR.
Yes but a thermometer measures temperature, and it doesn't measure heat.Yes, it is different than deep IR, which is EM radiation.What I'm saying is that two bodies can exchange heat even in a vacuum and without being in contact, through blackbody radiation, which is deep IR.Also , something can get hotter in a vacuum and being in contact with nothing, we know this because we can just heat it up with a laser. :D But it can also get colder as it radiates the heat away, and its temperature drops.I'm not sure how that works, I think the particles emit photons while they're moving , and loosing energy by doing this. :-/
 
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IR is better for burning VS other visible wavelengths because it does "wash out" what you're burning.
 




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