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ArcticMyst Security by Avery

Power calculations

Joined
Mar 21, 2011
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Hi guys

I'm new to this, but i've seen alot of post relating to the power of lasers and think a good way to visualize it is heating power ie temperature increase of water in 1 second.

I know C=Q/ΔT where C =Specific heat, Q =heat and T =temperature
and dimensionless heat capacity = C / Nk where n is number of molecules and k is the Boltzmann's constant
energy of photon = hc/λ where h is planks constant, c is speed of light and λ is wavelength

What i don't understand is how the labeled power corresponds to the energy of the photons or how to use this to calculate Q heat transfer.

Thnaks for you help
 





anselm

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Nov 22, 2010
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I don't know if this helps any, but go to this page and scroll down a little until you
reach the part where she uses a mug filled with water to measure the power
of her CO2 laser:D
Diane's Laser Page

In any case, I think you need an object immersed in the water that can absorb the
lase radiation and pass off the heat to the water, since the water itself has
a hard time absorbing the laser radiation directly.;)
 
Joined
Sep 12, 2007
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It might be right in its own way, but that's kind of a strange way to put it. I was always taught:

Q=CmΔT

All the same variables with the addition of mass m.
 
Joined
Mar 21, 2011
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in response to Cyparagon: I agree Q=CmΔT is a better/easier equation to use:thanks:.

In response to anselm: I was thinking more about how much energy is carried in the laser beam. Then i can build on this to calculate absorption in different materials, conductance and energy densities ( affect of lenses).

Cheers
 

BennyF

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Mar 14, 2011
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well you could use the equation E = n*e where n= the number of photons and e= the energy of the photon. Also you can use E = nhf where h= Planck's constant and f= frequency. P= E/t, P=nhf/t t= time for a time of 1s t is removed from the equation. P=nhf=nhc/l c= the speed of light and l= the wavelength.
 
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