Re: Light heating

From: Marshall Burns (
Date: Wed Apr 24 2002 - 21:50:30 EEST

This is not off-topic if the heating you are interested in is for inducing solidification, as in laser sintering or selective thermal curing of polymers.

Light causes heating (i.e. increased temperature) in materials when it is absorbed and its energy goes into exciting any vibratory modes of the material's molecules. Both wavelength (or equivalently, frequency) and intensity determine the amount of heating, as follows:

        -- The light frequency, together with the molecular properties of the material, determine how effectively the light can be absorbed.
        -- The intensity determines how much light is available to be absorbed. Intensity is not so relevant if the frequency is wrong for absorption.

Absorption of light by materials is a deep and fascinating subject in physics and materials science. A nice technical explanation is in the Feynman Lectures on Physics, Vol. 1, chapter 31 on refractive index. If you want to go deeper, you can read up on the complex index of refraction in Jackson's "Classical Electrodynamics". A fuller treatment, taking into account the nuances of any particular material you may be interested in, requires the tools of quantum electrodynamics and/or computational analysis.

Good luck with your research.

Marshall Burns

  ----- Original Message -----
  From: Yanyan Tang
  To: RP List
  Sent: Saturday, April 20, 2002 21:32
  Subject: Light heating

  Dear List,

  I know I might be wrong to ask a sort of off topic question here. But I know there are a lot of smart people over here. So please could anybody give me any hints about how the light energy converts to thermal energy or where I can find info for that. I am trying to figure out it is wavelength or intensity or some other character of the light that makes the light be able to heat things up. If anybody out there could help me about this, I would greatly appreciate it.

  Best regards,

  Yanyan Tang

  Graduate Student

  325807 Georgia Tech Station, Atlanta GA30332


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