# Why magnetic component of light is not shown in polarization diagram? Does polarization eliminate magnetic field?

So far I knew about light-polarization is like this ...

in an event of a plane-polarization, the polarizer-crystal does NOT separate the electric-component and magnetic component of the light. The magnetic component after polarization is just Not drawn to avoid some (?) complications. So ,

Fig 1. the vertical arrows is just an abbreviation showing the vertical electric field, and not showing the horizontal magnetic fields. (in fig. 1 the dot-sign indicates we're viewing the ray coming towards our eye). (In the right-side, realistic image, i did not shown double-headed arrow b'coz i've shown condition at one moment)

So, if we could draw the plane-polarization event including the magnetic field, it should look like this.

Fig 2. If we could show the magnetic field, it should look like this. Fig 2a when we would see from side, fig 2 b when we would see from front. (in fig 2b i didn't used double-headed arrow because i shown condition of one moment.)

I can't recall exact source from my memory... it would be my college chemistry classes.

Now a geology college-student is telling the above-thing is completely wrong. According to them,

The polarizing-crystal actually filters-out the magnetic-component and allows only the electric-component only, like this-

Fig 3. Only electric-component coming-in.

Both of us searched internet for hours make the dispute clear, but I could not display them any diagram that displays that , after being filtered through a polarizing crystal, the wave retains both the components. So they didn't believed this and stood on the same point (fig. 3)

So, My question is, which-one of the concept of linear-polarization (from above 2) is correct? If both is wrong, then what would be the correct concept?

• Your question seems to be getting answered, so I'd like to common on "(best if graphic)". There comes a point when you must either learn some of the math or you will be lied to by the visualizations that you think are helping you. Even in the above you are perilously close to that point. Commented Aug 12, 2016 at 18:38

The electric vector is usually taken as the polarization vector. The electric field exert force $-eE$ on the electrons of the atom and the electrons will get the acceleration $-eE/m$. The strength of the magnetic force $-e(v\times B)$ is ~$1/c$ times smaller than the force by electric field (where c is the velocity of the light). Almost all the properties of the light with matter comes from its interaction with electrons inside that matter. Based on these facts the direction of electric field becomes the natural choice of the direction of polarization.

The polarizers are the materials which has easy movement of electrons in one direction (pass direction) and restricted movement in perpendicular direction (block direction) resulting in more absorption in block direction (Such as wire grid). Hence light wave which has electric field parallel to the pass direction is passed.

Magnetic field will remain same until unless you are using ferromagnetic materials. It may be noted here that even if you choose a medium in which one of the field components is absorbed preferentially, as soon as the light leaves that medium (if at all it can leave the medium) the stronger component will reproduce the depleted component naturally such that their strength become equal (as in normal case).

I hope this will help

• Thanks for a new information, the impact of ferromagnetic media.
– user115953
Commented Aug 14, 2016 at 14:13
• when the charges start to accelarate shouldnt they also emit an em wave ? so why we dont get this wave out of the polarizer ? Commented May 17, 2019 at 15:12
• @adosar yes you are right. But this wave has same polarization as blocking wave and it may get absorbed or reflect (depending on the type of polarizer) same as blocked wave. Commented Jul 28, 2019 at 4:04
• @hsinghal so "inducted" em waves are absorbed or reflect from the neighboor molecules in the polarizer ? Commented Jul 31, 2019 at 10:23

You are (mostly) right, your geology friend is wrong.

As stated in the comments, an electromagnetic wave can not consist of only an electric nor of only a magnetic field. They go hand in hand.

• They all look ok to me. Which one is wrong, and why? Commented Aug 12, 2016 at 14:40
• 3rd wave also in forward (rightward). all waves are drawn in same direction. For each wave there are 3 arrows. one for E, one for M (or B) and one for wave motion. I forgot to give labelling on the right column on fig 2a
– user115953
Commented Aug 12, 2016 at 14:44
• @garyp oops, i think i read that third picture wrong, i thought that was the second one inverted. my bad, i'll edit Commented Aug 12, 2016 at 15:13

An electromagnetic wave always has an electric and a magnetic field. You cannot remove one and have the other still propagate.