# Why only electric field is considered in Wave optics?

1. Nov 5, 2012

### justwild

While studying polarization I came to a word "Electric field vector" and not "magnetic field vector". Then after reading certain references I came to know that it is electric field which is considered in wave optics.
Why is Magnetic field not considered??

2. Nov 5, 2012

### sugeet

According to the CED, that has developed; the E-field vector`s trajectory defines the parameter called polarization. If the tip of the E-field vector traces a specific trajectory then the wave is polarized(by definition), if it traces a random path we call it unpolarized light. The light intensity that we observe is the E-field intensity, then in our diffraction and interference also we consider the E-field intensity only

3. Nov 5, 2012

### DrDu

As rot E=-dB/dt you know B once you know E.

4. Nov 5, 2012

### andrien

In case of light,relation E=CB holds.You can see clearly,that B is 1/c times of electric field.Moreover,magnetic field has it's role in exerting the pressure on any surface.

5. Nov 5, 2012

### DrDu

only in vacuo.

6. Nov 5, 2012

### snorkack

The direction of magnetic field is normally determined by directions of electric field and wave propagation. And properties of medium?

Are magnetic and electric field required to be at right angles, in anisotropic medium?

7. Nov 5, 2012

### DrDu

E and B yes, while D and B are not necessarily perpendicular.

8. Nov 6, 2012

### andrien

Still B would be very small.That is what my point was.

9. Nov 7, 2012

### justwild

Thank you for all the answers.
Now what I know is that since polarization and intensity both depends upon E-field so in wave optics we are concerned with E-field only.
Moreover, according to andrien since the magnitude of magnetic field is c times less than the electric field so magnetic field is merely of any concern here.
So as far as magnetic fields are concerned they are there to produce electric fields which helps in EM wave propagation.

10. Nov 7, 2012

### snorkack

Also, substances whose magnetic permittivity is far from unity tend to be poorly transparent to high frequency electromagnetic waves.

How about polarization of low frequency radio waves in ferromagnetic materials which do not conduct electricity, like rocks? Magnetite is isometric crystal structure, so isotropic... which common substances are anisotropic ferromagnets AND transparent to radio waves?