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Semantics of EM spectrum

  1. Feb 16, 2013 #1
    I am a trainee science (specialising in physics) teacher. I upset my mentor a little bit by saying to a year 10 science class that there is "light" that people cannot see... by which I was referring to wavelengths of EM radiation that lie outside of the 400-700nm range.

    After the lesson, my mentor told me that I was wrong to use the term "light" when referring to wavelengths that we cannot see. He said that the word "light" refers only to wavelengths that we can see. He asked me to stop referring to invisible radiation as light. I was disappointed with this because:

    1) I felt my use of the word light was correct.
    2) I thought that it helped to communicate the idea that these other wavelengths of the EM spectrum are not in any fundamental way different from the wavelengths that are visibile to us - ie. I felt it helped to take the mystery or confusion away from what the EM spectrum is all about.

    Anyone care to offer their feedback?
    Last edited by a moderator: Feb 16, 2013
  2. jcsd
  3. Feb 16, 2013 #2
    I think your mentor is right.
    And not only because of word meaning, but gnosiology itself.
    It is important to introduce generalization as a new concept.

    Grotesque analogy: Would you introduce an "animal" as a bird, which not always can fly?
  4. Feb 17, 2013 #3


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    I think ultraviolet radiation is usually called ultraviolet light or UV light. We can't see it, but some insects can.
  5. Feb 17, 2013 #4
    I see a contradiction between the last two answers to the OP question.
    @Graniar basically says that light is just the , well visible spectrum but
    @Khashishi well ok UV can be seen by some insects then infrared can be seen by some animals , snakes can see infrared which they use for attack on prey.
    So when do we call light , light and when do we stop calling it light? Where does one draw the line at which frequencies?
    Or maybe we don't , I'll let some others speak about it.
  6. Feb 17, 2013 #5


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    This whole thing is a bit silly.

    If we say one cannot exceed the speed of light, does this automatically mean that only the visible part of the spectrum that is relevant? Does that mean that saying "visible light" is redundant?

    It is all in the context. In physics, "light" refers to electromagnetic radiation. Period.

    However, to the general public, "light" often means only the visible spectrum.

    You and your mentor need to come to some sort of an agreement on whether the message needs to be physically correct, or if it only needs to be correct in the non-technical sense. One only needs to open an undergraduate E&M text to know that "light" and "electromagnetic waves" have no distinction. So is the purpose here to teach the students the students to know that "light" is EM wave, or simply to reinforce the idea of "light" being the visible part of the spectrum?

  7. Feb 17, 2013 #6
    I'm with ZapperZ, and that SUDOnym's points 1 and 2 were both correct. My take is that the mentor in this case has assumed a common perception entailed a formal label. With respect to the analogy calling an "animal" a bird that can't always fly, consider that "animal" = light and "bird" = visible light. That completely reverses the analogy, and that, asZapperZ has pointed out, is exactly how textbooks tacitly characterize it.
  8. Feb 17, 2013 #7
    Well there are many analogies in which to put it, Could be a line of firefighters, some taller some smaller yet just because ones smaller you don't suddenly question is he a firefighter or not.

    I think you should talk to the mentor about this matter , sometimes the students have to educate the teachers, and does it really matter which way the teaching goes, as long as everybody gets a better understanding that's the goal to achieve.
    When it comes to learning we should put our egos and ranks aside I think.There have been some cases where I have told something my teachers didn't know either as their just human and can't absorb all the things that are being put ahead , even though in this case it's not something incredibly new rather a choice of ones own interpretation yet not always accurate.
  9. Feb 20, 2013 #8
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