Monochromatic and fully coherent light wave Wave, given essentially by the exp term, describes a We tackle those we have to learn a bit about polarization. We still have a bunch of open questions from above but before ĭon't mix up the power flux in W/cm 2 with the specificĮnergy measured in in Ws/cm 3or J/cm 3 that is contained in fields as shown above! It's time for an exercise to get some ideas about the numbers associated with light power and field strength! The average power delivered to an area is thus.Gives directly the power flux in W/cm 2 of an Wavevector k direction as shown in the figure above.Ĭos 2( kr - w t), the magnitude of the Poynting vector, S points in the direction of the propagation of the light, i.e.Simple number! You can buy a resistor with 377 W and wonder why it somehow reflects aīe that as it may, we now define a new vector S as follows: We justĬonnected vacuum, the nothing, with a defined property that can be expressed in a This is a bit strange if you think about it. This is an apt name since Z w does have the Z w= E 0/ H 0=( m 0 m r/ e 0 e r) ½ that is called the wave That this follows 'straight' from the Maxwell equations and is given by We do not yet know, how E and H are linked. Magnetic field in vacuum (in materials use D and B instead of E and Well, we (should) know how much energy density W =energy /cm 3 is contained in an electric or All of us who once experienced a sun burn (or shot down one of thoseĮvil alien space ships with a Laser gun) know that. For now you can use this link to get some ideas about the answers and, even better, you could do the I will go into details later whenever necessary.

The good news is: For most of what follows you don't have The bad news is: There are no easy answers for some of those questions. It's not very difficult to conceive and to How is this lightĮnergy transported by an electromagnetic wave?

Let's assume you know the electrical field E 0: how large is the magnetic field H 0 associated with it?īrings along is E Ph=h n.

How large (roughly) is it for one photon of a given

How large, in V/cm, is the electrical field E 0.

Is the electrical and magnetic field really in phase as shown above?.

How do I describe polarization in the particle picture?.

What happens if E 0 H 0 are not parallel to D 0 B 0,.

Can polarization be described by a vector? Could I just use a unit vector in E 0-direction?.

Then a few questions should come up, for example: In a Master study course, however, you now ponder the picture and the equations above for a

Usually we don't bother to go muchĭeeper at this point. H-field amplitude in z-direction given by H 0.E-field amplitude in y-direction given by E 0.Propagation direction= k direction= Poynting vector S direction= x direction here.With the relevant vector quantities, we see that in this case: Looking for example at a picture we had before but now augmented The electrical field vector (or the electrical displacement vector D in material) thus isĬontained in some plane (the polarization plane) that contains the direction of Light as a wave, by definition, is polarized since an arbitrary light wave can always be decomposed into plane waves describedĮ( r, t)= E 0exp and the corresponding expression for the magnetic field. 5.1.4 Energy Flow, Poynting Vector and Polarization 5.1.4 Energy Flow, Poynting Vector and

Intensity equation polarized light