Kirchoff's radiative balance law and polarisation of emitted light

[Mark.R]

I'm looking at a surface at an angle. Light reflected to me is polarised (Fresnel), does this mean light emitted to me from the surface is also polarised?

I've been told that ocean emission is polarised (when looking at an angle) because of Kirchoff's law of radiative balance (emissivity = absorptivity = 1 - transmission - reflection). They've told me that since reflection is polarised at that angle, absorption must be polarised and therefore emission is too.

But I don't see why it has to be and physically I don't see where it comes from. The only possible source I can see is something to do with the angle of observation. Can anyone help me?

 

[Naty1]

Try here: http://en.wikipedia.org/wiki/Polarized_light#Polarization_effects_in_everyday_life

 

[Naty1]

I think you mean Kirchoff's law of thermal radiation...

http://en.wikipedia.org/wiki/Kirchhoff's_law_of_thermal_radiation

 

[lalbatros]

Usually, both polarisations are not transmitted and reflected in the same way at a plane interface.
Therefore, the reflected light has a different polarisation mix than the incident light.

This is completely described by the Fresnel laws.
The Fresnel laws are a consequence of the Maxwell equations.

On wikipedia you can read the Fresnel laws in detail.

http://en.wikipedia.org/wiki/Fresnel_equations

There is a special angle of incidence, called the Brewster angle, where one polarisation (E field in the incidence plane) is not reflected at all. In this case, the reflected light has a perfect linear polarisation, perpendicular to the incidence plane.
See there for the details:

http://en.wikipedia.org/wiki/Brewster's_angle

The Brewster angle is a consequence of the Fresnel laws.
The Fresnel laws are a consequence of the Maxwell's equations.
The Maxwell's equations are the law of electromagnetism.

 

[Andy Resnick]

I'm looking at a surface at an angle. Light reflected to me is polarised (Fresnel), does this mean light emitted to me from the surface is also polarised?

I've been told that ocean emission is polarised (when looking at an angle) because of Kirchoff's law of radiative balance (emissivity = absorptivity = 1 - transmission - reflection). They've told me that since reflection is polarised at that angle, absorption must be polarised and therefore emission is too.

But I don't see why it has to be and physically I don't see where it comes from. The only possible source I can see is something to do with the angle of observation. Can anyone help me?

The emitted light may have a non-zero degree of polarization:

http://www.opticsinfobase.org/abstract.cfm?URI=ao-38-8-1384

Kirchoff's law is simply conservation of energy.

 

[Mark.R]

Thanks for the replies.

I'd already checked wiki and I can derive and apply the Fresnel equations (which is how I know reflected stuff can be polarised!) I think I didn't explain my question properly, but Andy has provided exactly the sort of derivation I'm looking for. Thanks Andy!