Polarization is a transverse wave property that describes its vibration direction, so that light can polarize suggests that it is a wave. because particles don’t do that. Yet a filter at an angle to a ray of polarized light reduces it but still lets some photons through unaffected, so its like particles that might hit an obstacle and might not. And a bigger angle lets fewer photons through, so a filter at 81º to the polarization plane lets 10% of them through. If light was a wave, an obstacle that 90% blocks it would weaken it entirely but instead, parts of it get through entirely. As usual, the evidence suggests that light can behave like a wave or a particle, so why is this so?
In the following discussion, quantum spin is taken to involve a:
a. Rotation axis. Around which the spin occurs.
b. Rotation plane. In which the spin rotation occurs.
Now let a polarized photon spin on its movement axis, as a bullet does, so it turns into all the planes that cut its movement axis (Figure 3.19). One might assume this alters its polarization plane, but typically it stays the same, so in general, the vibration direction of a photon doesn’t change as it spins in our space.
To understand this, consider a book sitting on its edge on a table so it is, say, ten inches tall. If the book is now spun in the rotation plane of the table, its height doesn’t change at all, as it is at right angles to table. Likewise, if the table is our space, spinning a photon within in our space doesn’t change its transverse vibration either. A photon that spins in our space, as assumed, needn’t change its vibration because it is at right angles to our space (Note 1). It follows that a photon can spin in our space without changing its polarization plane.
In contrast, turning a filter that blocks light polarized one way lets more and more light through until at 90°, it lets all the light though. Why then does turning a filter differ from spin turning a photon? In the example above, turning the book doesn’t alter its height, but does affect its width for a given direction. If the filter then acts like a wall that blocks a wave, turning the wall will block a wave less. Rotating a filter is then like turning a book to obstruct less (Note 2), while spinning a photon in our space doesn’t alter the wave amplitude or direction. Of course it isn’t that simple, as Chapter 4, matter fills many quantum directions not one, but the principle remains.
Why then do some photons pass entirely through a filter on an angle? Again, it is because a physical event is an all-or-nothing affair. The filter reduces the probability that instances get through it, but if one is detected, the entire photon restarts there. By the same logic, what passes through the filter is also the entire photon. A photon then travels like a wave because it is a wave, but is detected like a particle because processing waves always restart all the processing that is the photon.
Note 1. Let the photon’s wave amplitude be in a direction Q, at right angles to its polarization plane XY. Now if the photon spins in the plane YZ, this swaps its Y and Z values but leaves Q unchanged, as it is at right angles to that spin. It follows that a photon can spin around its movement axis X without altering its amplitude vibration, and hence its polarization plane.
Note 2. If Q is the quantum amplitude it reduces as Q.Cos(q°), where q° is the angle between that amplitude and the filter direction in quantum space, so at a 90° angle it has no value, as Cos (90°) = 0.