What color will burn stuff the best?

[sephiroth]

So, I was right. :yh:

 

[intrigue]

So, I was right. :yh:

Yep. I wanted to clarify the reasons. I liked your sea/cliff analogy.

 

[sephiroth]

:thanks:

It's just easier to understand when you give some example form everyday life.

 

[Damien]

Even though shorter wavelengths have more energy per photon, we measure laser output not in energy but in power (watts, milliwatts, etc). A watt is a defined as 1 joule per second. So you can see that power is the rate at which energy is created/consumed.

One watt of green is equal to one watt of violet in terms of power, which means that one watt of green equals one watt of violet equals one joule/second. Wavelength here is relevant only in it's ability to be absorbed by materials of different color.

Then different colors will absorb power differently, such as a battery?

 

[BIGDUFF]

i dont know but just asking if you have a 200mW green , red ,and blue is it not still 200mw kinda like which is heavier and pound of butter or a pound of suger there both a pound are all three not the same mw but reached at a lower effort like i said just a question cause im a newbie with a broke green ebaser and a 6x blue ray diode on the way so take it easy on me

 

[chipdouglas]

look at it like this.... ignore the 200mw part and lets say 50mw.... focus a red green and a violet to burning... now point each one at your arm... in my experience you will only be able to feel the violet one sting you. this goes back to the whole color absorption thing.

 

[sephiroth]

That's perhaps becouse your arm absorbs frequency of blue light easier. But amount of energy emited from all 3 laesers is equal if they have equal powers and work the same period of time.

 

[intrigue]

i dont know but just asking if you have a 200mW green , red ,and blue is it not still 200mw kinda like which is heavier and pound of butter or a pound of suger there both a pound are all three not the same mw but reached at a lower effort like i said just a question cause im a newbie with a broke green ebaser and a 6x blue ray diode on the way so take it easy on me

You are correct. The difference is in how well that light is absorbed by different materials (and thus, how much energy is absorbed). 200mW is 200mW, regardless of color.

Different colors reflect different wavelengths. For instance, a plant appears green since it reflects green light. It would be easier to burn this plant with a laser that is not green.

To Damien: You are on the right track. Materials of different colors will absorb different amounts of energy based on the color of the light. So a red paper will absorb more energy from a 1mW green laser than it will from a 1mW red laser, because more of the red light is reflected away. On green paper, this situation would be reversed.

 

[Ash]

I have done this experiment with 100mW of 405, 532, and 660.

The 405 burns fastest, then the 532, then the 660.
The shorter wavelength laser light is absorbed faster in most materials due to it's higher energy.

 

[chipdouglas]

That's perhaps becouse your arm absorbs frequency of blue light easier. But amount of energy emited from all 3 laesers is equal if they have equal powers and work the same period of time.

his main question isn't about power level.... it clearly states what color burns better... and the answer is ... there is no one answer... its all about color absorbstion. and when you get to high mw or even w's it becomes irrelevant.

michael

 

[intrigue]

I have done this experiment with 100mW of 405, 532, and 660.

The 405 burns fastest, then the 532, then the 660.
The shorter wavelength laser light is absorbed faster in most materials due to it's higher energy.

I'm not positive, but I believe it's because less light was reflected off of the material with the 405nm. It's difficult to say with certainty, because I don't know what you burned.

If you used 100mW for all three lasers, then they all put the same energy on the target (0.1 J/sec). If 405nm burned the fastest, it was simply because the material absorbed violet better than green or red. Keep in mind, the definition of a watt is 1 joule per second. A watt literally defines the amount of energy in joules over one second.

You are correct that photons at shorter wavelengths are more energetic (see my multiple posts above going into detail on the math behind this), but 100mW of 405nm and 100mW of 532nm both are 0.1 J/sec. The difference is what is absorbed, and that has to do with reflectivity, not wavelength.

his main question isn't about power level.... it clearly states what color burns better... and the answer is ... there is no one answer... its all about color absorbstion. and when you get to high mw or even w's it becomes irrelevant.

It's not irrelevant, because you need the appropriate amount of power to burn certain material. You certainly aren't going to be cutting 2x4's in half with a 100mW laser. So, what power do you need? That depends on the wavelength that this particular wood absorbs best (lower wattages are needed for more readily absorbed wavelengths).

 

[sephiroth]

And to conclude this discussion:

If you have perfectly black stuff you can equaly burn it with any laser (if they have equal power). :crackup:
This black stuff will absorb all of energy emited from laser.

@ chipdouglas

I know that his main question isn't about power level, but if you have 5W laser (of any color) it will burn stuff batter than every 5mW laser. So I suppose that lasers have equal power.

 

[chipdouglas]

sephiroph and intrigue you are new here so i will be kind... it is irrellevent when you get into watts... and as about lower mw ask member dguin he has been able to light matches with his 30mw violet... to my knowledge no other member here is doing that with any other color laser.

also for the record... math/science results are a hell of a lot different than real world results.. if you stick around long enough you will learn this.

thank you
michael

 

[intrigue]

sephiroph and intrigue you are new here so i will be kind... it is irrellevent when you get into watts... and as about lower mw as member dguin he has been able to light matches with his 30mw violet... to my knowledge no other member here is doing that with any other color laser.

also for the record... math/science results are a hell of a lot different than real world results.. if you stick around long enough you will learn this.

thank you
michael

I'm not sure what you are getting defensive for, my only response to one of your posts proves your point with regard to dguin. If you read and understand my previous posts, you would see that due to reflectivity, a violet laser WOULD ignite a Red match at lower wattage than a green or red - but it isn't due to the extra energy per photon at that wavelength.

And yes, high wattage is irrelevant when burning matches, but It was used in
an example, and you took it out of context. I can say that if you are trying to burn metal, high wattage will be relavent.

I'm sorry if you felt I was attacking your observations, I wasn't. I agree with them, and was trying to show the mathematical basis for them to help people understand the "why", which I feel is just as important as the observations. If you don't at least try to understand "why", you are just playing.

This science has been proven with decades of laser research, it is wise to not dismiss it so easily.

 

[chipdouglas]

well intrigue just because i have an answer for your counter statements to mine it doesn't make me defensive...... edit here... i had a long rant typed but i went back and read again..

i am not saying violet has more energy per proton. i am not saying violet is stronger...i am clearly answering the question asked in the title. "which color burns the best.

if you wanna get technical thats fine.... but when a new member asks the question it is assumed for "pointers". and for pointers the answer is violet.

michael

 

[sephiroth]

Hey guys, probably we are all right.

Yes, it's true that intrigue and I are new her. I'm here because I would like to make my own laser. I've never done this before so I realy didn't now how to do it until i became a member of this forum. But I do know what laser is and I do know a theory.

As I can see intrigue also knows theory and it is true that science has been proven with decades of laser research.

BUT my previos posts don't mean that you can't light matches with 30mw violet laser. It means that these matches absorb violet light easily. So, these matches definitely were not violet or blue becouse that material would reflect all (or the most) of violet light and not absorb it. In my opinion these matches were red or brown or any other "darker" color.

Do you know what was the color of these matches? That would solve our problem. :yh:

And one more thing. If I'm not right I would be happy someone to explain and clarify these things. In that way we all learn something new. :yh: