# Unpolarized light, spherical wavelets and Photons

Before I get to the core of my question, I would like clarify my understanding of unpolarized light. Below are 2 images of unpolarized light from Google:

The first one seems to be in accordance with my understanding- the electric fields (and magnetic fields) have different planes of vibrations.

In the second one however, the unpolarized light seems to consist of 3 different light waves, each having different planes of vibration. But these vibrations seem to be constant for each wave. Thus, they would interfere and the resultant wave would contain vibrations in one plane. So I feel that this representation is not consistent. Please correct me if I am wrong.

Light bulbs produce unpolarized light, right? And these travel in the form of spherical wavefronts (concentric spheres). Based on my understanding, I have sketched the following.

What I have depicted is a crest of a spherical wavefront. (I have shaded the corners to make the wavefront look like a sphere.)

1) Are the orientations of the electric field and magnetic field constant for a given wavefront? (i.e.), for a given wavefront, does the plane of vibration of the electric field remain the same?

2) Is the light unpolarized because the orientation of the electric and magnetic fields are different for each wavefront (as shown in my sketch)? Or because the plane of vibration changes each instant for a given wavefront itself?

3) How can I relate all this to a photon of light? Does one photon mean the same thing as one wavefront?

Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This 3D animation shows a plane linearly polarized wave propagating from left to right. Note that the electric and magnetic fields in such a wave are in-phase with each other, reaching minima and maxima together.

An unpolarized wavefront will be composed by a large number of such waves, incoherently.

1) Are the orientations of the electric field and magnetic field constant for a given wavefront? (i.e.), for a given wavefront, does the plane of vibration of the electric field remain the same?

The two pictures above try to convey that unpolarized light is an incoherent superposition of an "infinite" number of polarization planes. The one showing only three to explain how to make a polarized wavefront.

The plane of vibration is the same for a given angle in a coordinate system, hypothetically picking up a polarization plane. It is all mathematics

2) Is the light unpolarized because the orientation of the electric and magnetic fields are different for each wavefront (as shown in my sketch)? Or because the plane of vibration changes each instant for a given wavefront itself?

For a given angle mathematically there is a plane of polarization. That is why the slits in the second picture pick up a polarized wave front.

3) How can I relate all this to a photon of light? Does one photon mean the same thing as one wavefront?

Here is how polarized light depends on the photon spin for circular polarization, photons can only have spin +1 or -1 to their direction of motion:

See my answer here for a discussion.

• Is my representation of electric and magnetic fields in the sketch correct? Commented Dec 15, 2018 at 11:12
• I'm sorry.. I've been using the phrase, 'plane of vibration' wrongly. I'll make an edit to my question Commented Dec 15, 2018 at 11:34