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So my question is light travel as wave, so light energy is basically increasing and decreasing electric and magnetic field? How do I visualize it?

Qmechanic
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dark silence
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5 Answers5

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A very short answer, followed by a suggestion.

I can only tell you how I visualise it in wave terms, which is the standard textbook model, but I don't think there is a better way of describing it.

enter image description here

A static picture of an electromagnetic wave is:

From Wikipedia Electromagnetic Waves

enter image description here

The electromagnetic waves that compose electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The electric and magnetic fields in EMR waves are always in phase and at 90 degrees to each other.

My suggestion is that you look at these images, and read the Wikipedia article, then post a more specific question on what aspects of the visualisation you don't follow.

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you visualize it when those fields interact with the photoreceptors in your eye, and starting a clear chain reaction whose ultimate purpose is to alert you of any potential changes in the environment

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    I'm not sure if when the OP said "how do I visualize it" they meant "how does my eye detect it". – M. Enns Jul 31 '16 at 20:27
  • The 0P wants to know what this wave looks like as it travels from point A to B. I think everyone has trouble visualizing a wave. It makes more sense if you picture individual oscillating photons. If a single photon traveled 1,000,000,000 miles as a wave how big was that wave?? And did it travel every direction in the universe? That makes no sense. I would picture a photon oscillating at a certain frequency as it travels along at the speed of light. The more the photons the more intense. – Bill Alsept Jul 31 '16 at 21:08
  • I think the OP is asking, How do electric and magnetic fields interact to produce electromagnetic waves? – sammy gerbil Jul 31 '16 at 23:04
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Imagine throwing a stone in a pond. You'll now see waves moving away from where the stone dropped. A pond is a 2D plane, while EM waves travel in 3D. It would behave much like in the pond, but the waves would move away from the source in a spherical way.

The field is increasing and decreasing so theoretically the beam/field of light should have observable dark and light spots. We cannot see this because the frequency of light is roughly 500 THz.

It would be an interesting experiment to proof that these dark spots exist because if they don't, our theory of light and electromagnetism is wrong.

progonkpa
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Visualization of light waves and radio waves are explained below based on “Planets and electromagnetic waves”. Light waves or rays interact with electric fields of electrons in a solar cell to produce a disturbance in electrons so that electricity is produced. In a tungsten bulb, electrons try to move with very close distance because of a voltage, and at the same time the electric fields of these electrons repel them. So, light energy is released. Light energy is associated only with electric fields. Visualize a light wave as electric component wave. Moving electrons have magnetic fields. Radio waves interact with magnetic fields of moving electrons, and disturb the moving electrons to make variations in current. Radio waves are associated only with magnetic fields. Visualize a radio wave as magnetic component wave. No one practically observed combined form of magnetic field type and electric field type of waves with common wavelength. In Hertz’s experiment, it happens that both light waves and radio waves are released but not with common wavelength. Some researchers do not consider microwaves as electromagnetic waves, because their velocity in vacuum is less than the velocity of light in vacuum.

iruthayaraj
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  1. In the above pictures there is drawn only the half of the electric and magnetic field component of light. It would be better to draw the north and the south pole of the magnetic field component as well as the full potential difference between plus and minus of the electric field component.
  2. The amplitude of the electric and the magnetic field component of light was never measured. And the electric field of a charge is defined as infinitely extended. But for the definition of light as a wave the amplitude has to be defined. So the square of amplitude was interpreted as the intensity of the given light. And the infinity was explained by the way, that light is a disturbance of an overall existing EM field.
  3. The phase dependence of the electric and the magnetic field components - their shift or no shift - for a laser beam as well as for single photons (if one think in photons) was never measured. For radio waves, which one make from accelerated electrons and by this made by a huge number of photons, for the reasons of discovered EM induction the electric field of the accelerated electrons in the antenna rod bear a magnetic field and this field bear an electric field and so on.

Following this points a sketch of a radio wave in the near field has the next form:

enter image description here

It is from some interest to show what is the discovery property of spin for an EM wave. It could be seen from the last sketch that there is a asymmetry in the relation between the directions of the electric und the magnetic field component. The blue and red arrows (representing the magnetic B-field and the electric E-field) follow each other anti-clockwise if one have a look in the direction of propagation. There is exactly one other possibility of arrangement of the field components. This shown in the second sketch:

r

For more clearness of what is an EM radiation, a photon and a radio wave see What is the relation between electromagnetic wave and photon?.

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HolgerFiedler
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    I think the two picture are false, the E and B field should be in phase as in the picture in count_to_10 answer. The "spin" of EM waves comes from the phase between the two normal components of the E field, not between the E and B fields – EigenDavid Aug 02 '16 at 10:41
  • @David "Following this points a sketch of a radio wave has the next form." How do you think the near field radiation looks like? – HolgerFiedler Aug 02 '16 at 12:14
  • @David https://commons.m.wikimedia.org/wiki/File:Dipole_xmting_antenna_animation_4_408x318x150ms.gif#/search – HolgerFiedler Aug 02 '16 at 12:34
  • It's not clear in your text that you are talking about the near field (but yes in the nearfield E and B are out of phase). When one talks about radiation, one refer usually to the far field. What you say is not wrong but I think it can really confuse OP. – EigenDavid Aug 02 '16 at 12:47
  • @David what are the two components of the E field? – HolgerFiedler Aug 02 '16 at 13:27
  • you mean relatively to what I said :"...between the two normal components of the E field..." ? – EigenDavid Aug 02 '16 at 14:01
  • @David Yes, that is what I ask you to explain – HolgerFiedler Aug 02 '16 at 14:40
  • I simply mean that the E field can be decomposed in two components in a plane perpendicular to the direction of propagation. The relative phase between those two components tells you if you have linearly, circular or whatever kind of polarization. From your sketch an explanations it seems to me that you say that the spin/polarization character of the wave comes from the relative phase between E and B – EigenDavid Aug 02 '16 at 14:50
  • The spin has exactly two values. How do you match that this your countless values of the spin in your interpretation? – HolgerFiedler Aug 02 '16 at 14:57