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B Want accurate cartoons of EM Waves

  1. Apr 11, 2017 #1
    If you were trying to explain to kids how EM Waves really look in nature, what would you show? None of these common graphics below are perfect. If you wanted to show comprehensive depiction of transverse EM Waves from the sun, from a laser pointer, from a radio / wifi transmission tower, how accurate are these?

    tower2.jpeg
    1. Most common wifi logo also most misleading and looks like nothing.

    wifi-area1.jpeg 2. Better wifi cartoon but wifi signal looks like Longitudinal Sound Waves, coming at you in same direction as Force or Motion. Missing are Electromagnetic Transverse Waves that follow Right Hand Rule.

    transverse1.gif

    3. Above Transverse depicts EM Waves, but most cartoons of EM Waves from sun or star fail to show full Right Hand Rule or Magnetic Field 90 degrees from Electric Field perpendicular from Direction of Motion, so kids again think EM Waves from sun must be Longitudinal hitting your face in direction of Motion not Transverse which radiate 90 degrees from Motion.

    righthand1.jpeg
    4. Right Hand Rule is great for kids but I never see it applied to wifi logos.

    wave2.gif
    5. Many EM Wave graphics like this one are great explaining how they move but are really hard to imagine in nature. I imagine water ripples radiating away from pebble thrown into pond, but that fails to capture whole EM wave, like which ripple is magnetic and how is it 90 degrees perpendicular from electric?

    nasa1.jpeg

    6. This NASA video is great explaining EM spectrum, and above graphic is great showing various waves hitting us constantly, from sun, TV, phone, microwave, etc. But above waves don't show right hand rule, so how could we add magnetic 90 degrees from electric waves and what would that look like?

    emwave1.gif

    7. I like above transmission of radio wave better than other wifi logos, as this clearly shows wavelength amplitude is 90 degrees perpendicular to Direction of Motion, so that helps picture how it must look in nature. It also looks like a real image from an Oscilloscope.
    emwave3.jpeg

    8. I like above photo suggesting transmission tower (or star) source in center, with EM waves radiating out in concentric rings, yet within each ring we see 90 degree perpendicular pink and blue lines suggesting Electric Field and Magnetic Field, so this image is more accurate than a typical wifi logo.

    Since images only capture one second in time, I have trouble imagining how EM waves look over time as they radiate out from sun or wifi tower, 90 degrees from Direction of Motion. An oscilloscope captures radio waves AM amplitude and FM frequency, but what do EM waves from the sun look like over a minute?

    Do you know better, more comprehensive images or videos? None of these are good enough.
     
  2. jcsd
  3. Apr 11, 2017 #2

    sophiecentaur

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    Gold Member

    Personally, I would say that suggesting that EM waves actually "look like" anything, would be to open a massive can of worms. That is unless they happen to be light waves - in which case we don't see the waves - just the effects.
    If you haven't got it all totally sorted in your mind, you risk getting asked questions that you just cannot answer without getting in deeper and deeper. Kids are very literal and will grab onto any half baked model and try to apply it to take themselves further down blind alleys. You really have to begin with a massive caveat about the fact that EM waves are not like anything they have come across but that water waves (etc) have some common properties.
    I understand your problem with Figure 2, which could suggest that the waves are longitudinal but, otoh, EM waves are not the slightest bit like the wiggly things in the 'room full of waves', either. You need to keep it deliberately airy fairy until they can handle the notion that those side to side diagrams all refer to Field Vectors and that nothing actually wobbles from side to side in EM waves. The Roomfull of Waves is very good for the message that there are all wavelengths passing through a room (rather than 'hitting you'.
    I sympathise with the fact that you may feel pressured to deliver a Syllabus that was constructed by people who may not have thought it all through. (This applies for all ages of pupil)
     
  4. Apr 11, 2017 #3

    jtbell

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    Staff: Mentor

    See this old post of mine for a snapshot diagram and instructions for how to create a complete animated picture.
     
  5. Jul 11, 2017 #4
    Wikipedia Antenna article has these 2 ani.gifs which are helpful:
    https://en.wikipedia.org/wiki/Antenna_(radio)
    Still no great ani.gifs to picture EM Waves in nature but these are better than any static drawings. Missing are FM Frequency Modulations or AM Amplitude Modifications of these radio waves that turn them into music. Even if kid can picture this in nature, final mindblower is all this motion is happening at speed of light! Please post better ani.gifs if you find any!

    Dipole_xmting_antenna_ani.gif
    1. Dipole Antenna Transmitter transmitting radio waves
    Dipole_receiving_antenna_animation.gif
    2. Dipole Antenna Receiver receiving radio waves
     
  6. Jul 11, 2017 #5

    davenn

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    that's irrelevant in the overall view of the EM wave

    the top one of those 2 animations is pretty good ... what more do your want ?
     
  7. Jul 12, 2017 #6

    A.T.

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    What's even better for kids than animations are interactive applets they can play with, like this one:

    https://phet.colorado.edu/en/simulation/radiating-charge

    You might find more on this site.
     
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