What does a light wave look like?

The only models I can seem to find online are 2D waves, they just look like sin() graphs.

I have seen the models of the two components of "light waves" (electric field and magnetic field) and they are represented on a 3D Cartesian coordinate system, but they are still just two 2D waves.

enter image description here

Surely light isn't really FLAT like this is it?

I guess I have always assumed it pules out in all directions greater then lesser as it travels, giving off the shape that you see during a sonic boom:

enter image description here

I have drawn what I picture to be a 3D model of the electric field of a light wave as it travels from left to right:

enter image description here (cone image from: http://www.presentation-process.com/images/3d-powerpoint-cone.jpg)

Is this an accurate representation of what the 3D radiation emitting from a light beam looks like, like a 3D wave? (Obviously it would be more wavey, using a 3D cone graphic to create this diagram caused the edges to look spiked and sharp, a better object to use would have been something like a bullet (3D parabola) but I'm not the best with photoshop).


Also, if this is a somewhat accurate model of light wave pulsing in 3D, what does the magnetic wave look like in model form? Do they just overlap with possibly a slightly larger or smaller amplitude but the same maxima and minima locations along t (x-axis in my model)

  • Well, it doesn't look like anything (i.e., you will never be able to see a light wave), but your "flat" pictures probably are closer to the truth if you think about what plane polarization means. en.wikipedia.org/wiki/Polarization_(waves) – Solomon Slow Jul 15 '15 at 18:53
  • @jameslarge haha yeah I meant more towards what a 3D model would look like, not the light itself xD Thanks for the link, I'll read into it! – Albert Renshaw Jul 15 '15 at 19:10
up vote 4 down vote accepted

The first 2-D image you posted is a typical simplification for teaching purposes. In it, they use the height of the sine wave to represent magnitude, and the directions of the sine waves to show how the fields point relative to each other. The light itself however is not itself at all cone-like. You have to imagine this sine wave existing at multiple points in space, not localized in this cone-like volume. This can be difficult to visualize.

A common method for visualizing these kinds of fields is a 3-D vector field plot.

vector field plot of light

Length or colour will typically correspond to amplitude, and the arrows show direction of the electric field. The magnetic field is always perpendicular, and the amplitude is proportional, so there's little sense in plotting both together. This one I've included shows how the field actually permeates a volume.

Out of interest, here's a gif of dipole radiation. This is just a 2-D slice of the field, and doesn't show vector direction, but is a very good visualization of a more real-life kind of radiation. Colour corresponds to magnitude in this case.

enter image description here

  • Nice animation graphic. What did you use to do that? Now the challenge---show the magnetic field in the same animation. That should eat up the rest of your summer! – Bill N Jul 15 '15 at 21:27
  • I stole it from the Wikipedia page on dipoles. I don't know what software they used to make it. Fortunately, the magnetic field is proportional to the electric field, so the colour represents the magnitude of either. Summer saved. – David Jul 15 '15 at 21:49
  • @David so according to your first image it actually is like a wave, just across many parallel cross sections making like the kind of wave you would see in a wave pool? So if this is the case if I shoot a laser onto a perpendicular wall it will hit at one spot, and then if I move it further away but keep it at the same height and what not (just slide back on z-axis) the light will hit at a higher or lower spot? – Albert Renshaw Jul 15 '15 at 22:40
  • Still trying to wrap my head around it O:) thanks for the animation, seeing dipole radiation is cool, is light a dipole? Or does it radiate off in every direction evenly. (I know magnetism is dipole and light is electromagnetic so I would think the "electro" radiation part may not be dipole) – Albert Renshaw Jul 15 '15 at 22:40
  • That's a good way of putting it, similar to a wave in a pool but across many cross sections. If you could measure the wave at a particular height, it would look similar to a wave on a pool. Light itself is not a dipole. Light tends to radiate in most directions evenly, but this isn't completely true. There will be directions where the radiation is weaker or nonexistent, like you can see in the gif. The reason this is called dipole radiation is because it's caused when you take a magnetic or electric dipole and oscillate it. This is similar to the pattern a simple straight antenna produces. – David Jul 16 '15 at 15:48

It highly depends on wavefront shape. And wavefront depends on the source. If your source is a star and you are far from it and detect the wave, the wavefront is planar enter image description here enter image description here There are many another wavefront shape for a different source. These are only the most common

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