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Electromagnetic Radiation and Heat Transfer

  1. Apr 29, 2010 #1
    I'm trying to explain heat and electromagnetic radiation to a group of middle school age kids. Would it be appropriate to describe heat as light that our eyes may not be able to "see" due to its wavelength, but that the nerves in our skin can percieve it as an incrased teperature? I'm looking for a good way to start a discussion of EMR.
  2. jcsd
  3. Apr 29, 2010 #2


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    Well you could briefly introduce them to the electromagnetic spectrum. Then say how the heat from the sun is transmitted through IR waves which falls out of the visible spectrum. So we can't see it, but it affects our bodies, like the wind.
  4. Apr 29, 2010 #3
    That is a great subject for kids. I think that you should make it clear that radiation is radiation is radiation. Light is what we see with our eyes which is always what x-rays are and microwaves, and the heat that comes from the sun. So many non-physicists do not understand this because they are never informed at a young age.

    A common question is going to be why lower frequency radiation heats us up and the higher frequency we can see does not burn our eyeballs up.

    Lower frequency radiation resonates with water molecules causing our skin to heat up.

    Visible light has too high of a frequency, like trying to shake a pendulum very quickly and it does not move, but you move nice and easy and it gets a huge amplitude.

    Visible light resonates with the detectors in our eyeballs however, they are like very short pendulums.
  5. Apr 29, 2010 #4
    Thanks for the help. Part of the problem, I think, is that there is a preconcieved notion that for something to have an affect on us that we can feel, it must have some solid physical presence. Kids can easily grasp that things like water or wind are made up of tiny particles that they can feel if enough of them come into contact with our skin. Radiation always seems so non physical in this context. Does this make sense? Heat and light, gamma rays, and x-rays, infrared and ultraviolet, frequency and wavelength are really hard to grasp for learners (not just kids). The question ultimately becomes something like: "What is it really that is hitting my skin and giving me a sunburn?" or "What do you mean wavelength? Are those photons leaving the sun and bobbing up and down through space till they hit my arm?" These are actual questions that I'm struggling to answer.
  6. Apr 29, 2010 #5
    We are all struggling to answer those questions, welcome to the club.

    I think what is important is getting the kids to start asking these questions, you have already done your job!
    Last edited: Apr 29, 2010
  7. Apr 30, 2010 #6

    Andy Resnick

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    What about re-creating the discovery of infrared radiation? Pass sunlight through a prism, and move a thermometer from the blue to the red and then past the red- the thermometer will register a change in temperature, even though you can't see any light.
  8. Apr 30, 2010 #7
    Which makes me wonder. Why does mercury heat up quicker with lower frequency light?
  9. Apr 30, 2010 #8
    Because red is hot and blue is cold! Everyone knows that...

    J/K, I just couldn't resist.
  10. Apr 30, 2010 #9
    It must be friday.
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