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Quick Science Questions from a Science Numpty

Discussion in 'Science' started by Trebaci, Feb 26, 2011.

  1. I posted this elsewhere but think the questions kind of got lost, so I'm trying with a new thread. Please think of me as a science numpty but with an eager willingness to learn and who will be grateful to anyone for answers to these and possibly later questions.
    Okay... first two science questions from a numpty regarding waves in the electro-magnetic spectrum.
    1. Is the wave length constant?
    Visual representations incorporating a degree of perspective can be interpreted as showing that waves start off smaller and closer together, becoming longer and further apart as they reach earth. Is that, though, a distortion, and does a particular form of energy have a constant wavelength from source?
    2. Would it be fair to refer to the sun's energy as 'pulsing'?
    Your expertise will be much valued.
     
  2. I posted this elsewhere but think the questions kind of got lost, so I'm trying with a new thread. Please think of me as a science numpty but with an eager willingness to learn and who will be grateful to anyone for answers to these and possibly later questions.
    Okay... first two science questions from a numpty regarding waves in the electro-magnetic spectrum.
    1. Is the wave length constant?
    Visual representations incorporating a degree of perspective can be interpreted as showing that waves start off smaller and closer together, becoming longer and further apart as they reach earth. Is that, though, a distortion, and does a particular form of energy have a constant wavelength from source?
    2. Would it be fair to refer to the sun's energy as 'pulsing'?
    Your expertise will be much valued.
     
  3. blazer

    blazer Star commenter

    Yes the wavelength stays constant if both the emitter and receiver are stationary. (Red shift). So a specific bit of UV say leavin the Sun will reach the Earth with the same wavelength.

    The energy output from the sun does seem to change with time sometimes going up sometimes going down. However I would think of a regular pattern when I think of 'pulsing'.
     
  4. Profound thanks, Blazer, for your answers.
    In terms of an illustration, then, I'm assuming that a wave expressed in, for example, 1 cm waves, is going to contain 1 cm waves from point of emission to point of reception? I'll take it as a yes if you don't respond - no wish to take up more of your time than necessary [​IMG]
     
  5. blazer

    blazer Star commenter

    Yes that is correct.
     
  6. My sincere thanks again, Blazer. Your help has been much appreciated.
    For what it's worth, I suspect that in the past some confusion has been caused by designers' attempts to include distance perspective in their renditions of waves, and again, just possibly, by the frequent illustration which aims to show variations in wavelength using a single line.
    Anyway, you've been a great help and I'm very grateful.
     
  7. Thank you, RW
    I appreciate the input.
    Pulsing.... I was 'feeling around', I think, for some sort of visual image that I could use to deal with the 'travels in straight lines'/'travels in waves' thing that I think some students have difficulty with. I've come up with a group of animations which seem to make sense (with Blazer's help and now your own, it at least, now, makes sense to me :), and I'm quite confident they're okay.
    Interested that you mention 'pulsing' in relation to 'variation'. My thought was that if there were a 'pulse' it would be so rapid and/or continuous that there'd be no discernible variation, except perhaps in the form of the waves that reach us.
    I should stick to Star Trek, clearly. I'm glad you guys who actually understand all this are out there.
    Very best wishes to you,
    R

     
  8. Supplementary question, if anyone is interested [​IMG]
    Clarification, anyway:
    Longitudinal waves v Transverse waves. If I understand the text books correctly (and I probably don't) most if not all of the energy we receive from the sun arrives in the form of transverse waves because longitudinal waves require particles in order to move around and won't pass through a vacuum?
    If true, does this mean, as it appears to, that longitudinal waves don't have their origin in the sun at all, but are only produced by processes on earth?
    Does the sun generate longitudinal waves that just never reach us?
    I've seen heat and light referred to as being transverse wave forms and sound as longitudinal. I'm not clear, from looking at standard EMS diagrams, but it appears as if all the radiation from the sun may be transverse? It appears that they must be, yet I know I may be getting hold of completely the wrong end of the stick.
    Any thoughts or observations would be welcome.
    R
     
  9. MarkS

    MarkS New commenter

    Hi there,
    All electromagnetic waves are transverse - the radiation from the Sun is EM so therefore transverse. The form of EM radiation we are most familiar with is visible, light but we also receive significant UV, IR and other forms too.
    Be careful when you use the word 'heat'...the 'heat' from the Sun is the energy carried by the EM waves, and we predominantly feel this from the IR component of the Sun's radiation. IR doesn't pass through water vapour easily, which is why it feels cooler when cloud passes in front of the Sun...we don't receive the IR.
    Heat energy really means the microscopic kinetic energy of particles, and this can be transferred in various ways, including by emission of IR radiation.
    Hope that helps!
    Mark
     
  10. Hello Mark
    and yes, it helps a great deal. I suspected something of the kind, but it certainly doesn't come across in the classroom. As far as the kids I'm working with are concerned, they're 'doing the Electro-Magnetic Spectrum' and it feels, in a way, as if 'longitudinal waves' have almost been dropped in at random. Will take a careful note of the 'heat' reference too [​IMG]
    Very much appreciated.
    Richard
     

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