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Have a look at the image below, enter image description here

It depicts Electric and Magnetic field components of electromagnetic wave.

I'm a bit confused about whats happening here.I mean is the electric field changing with time or position and what do the waves actually represent(the intensity or direction)...

Divyanshu
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    Possible duplicate of Understanding the diagrams of electromagnetic waves – Stéphane Rollandin Jan 09 '18 at 16:15
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    Red and blue lines represent the instantaneous locations of the tips of the electric and magnetic field vectors corresponding to points along the x-axis. The fields oscillate in both time and space--that's what a wave is (think of a wave travelling along a string). – Ben51 Jan 09 '18 at 16:18
  • Ultimately light is made of billions of individual photons. A field or even the term wave are many coherent photons propagating at the speed of light. The photons are oscillating as they travel along and create the pattern depicted above. – Bill Alsept Jan 09 '18 at 19:06
  • @Bill Alsept Are you suggesting that photons follow sinusoidal paths?? –  Jan 10 '18 at 01:01
  • @Pieter Not exactly, it would be more symmetric than that. I’m suggesting the photon expands and contracts in a spiracle pattern as it travels along at the speed of light. A photon with a 500 nm wavelength is actually oscillating in and out about 600 trillion times per second and has nothing to do with waves. – Bill Alsept Jan 10 '18 at 01:18
  • @BillAlsept A photon as everything to do with waves. A photon is not a particle. You say that it is oscillating. What is oscillating? – garyp Jan 31 '18 at 14:24
  • @garyp If photon is a particle and the oscillation is described as I did above. What cannot be described is a light wave. – Bill Alsept Jan 31 '18 at 15:35
  • Our universe is described as an expanding spherical shape and there are many theories describing it as oscillating between expanding and contracting. This type of oscillation is not that hard to visualize. Now just imagine that oscillation happening 600 trillion times per second and you have a photon characterized with a 500 nm wavelength – Bill Alsept Jan 31 '18 at 16:39
  • @BillAlsept So the oscillation associated with a photon is the expansion and contraction of the universe? I don't think you mean that. What is oscillating? A photon is not a particle in the everyday sense of the word. In the usual sense of the word, a particle has a location. A photon doesn't have a location, although it's location can be narrowed down to a region. – garyp Jan 31 '18 at 16:50
  • No I said a photon oscillates like some theories describe our universe. That is different than what you said. Also my idea not only can calculate any light phenomena but it can be physically described. A wave cannot – Bill Alsept Jan 31 '18 at 16:53

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See the animation below. A light ray is travelling along the $x$-axis, the arrows are the vectors for $E$-field (orange) and $B$-field (cyan) at the corresponding position $\mathbf{r}=(x,0,0)$. The wave function can be written as follows:

$$\mathbf{E}(x,0,0,t)= E_0 \sin \left( \dfrac{ct-x}{\lambda} \right) \, \mathbf{e}_{y}$$

$$\mathbf{B}(x,0,0,t)= B_0 \sin \left( \dfrac{ct-x}{\lambda} \right) \, \mathbf{e}_{z}$$

where $E_0=cB_0$ or precisely $\mathbf{k}\times \mathbf{E}=\omega \mathbf{B}$.

enter image description here

Ng Chung Tak
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The picture gives you a snapshot in time of both the directions and field strengths of a plane electromagnetic wave propagating in x-direction. The arrow indicates the propagation direction of this wave with time, which would give you a shift of the field strength patterns in positive x-direction by $\Delta x=c\Delta t$ where $\Delta t$ is the elapsed time after the time of the snapshot.

freecharly
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