QR3.2.1 Light is a Wave

Figure 3.5. The electromagnetic spectrum

Maxwell’s equations describe light as a vibration in an electromagnetic field that sets imaginary potentials at right angles to its polarization. When this wave vibrates slowly the result is radio waves, faster vibrations are visible light and very fast vibrations give x-rays and gamma rays (Figure 3.5). The light we see is the part of this spectrum that vibrates about a million-billion times a second, gamma rays are a billion times faster, while radio waves vibrate only a few times a second. For simplicity, from now on the term “light” will refer to any electromagnetic vibration because the only difference is the frequency.

Newton’s optics describe a ray of light as traveling on a single movement axis. We now know that such a ray includes photons polarized in many directions but can use filters to polarize a ray one way. Modern lasers can even produce a pulse of light of one frequency in one polarization plane that travels on one axis, i.e. one photon.

Using such techniques, we can produce rays of polarized light that are out-of-phase, so the crests of one occur at the troughs of the other. The result is two rays that are separately visible but in combination they give absolute darkness. The photons cancel each other out just as out-of-phase waves do. This light + light = darkness is only possible for waves. Note that flashlight beams can’t do this because they aren’t polarized. This result proves that light really is a wave.

Figure 3.6. A circle maps to a sine wave

We even know the type of wave. Light is a sine wave, which in mathematics maps to a circle extended (Figure 3.6). If a pointer turning like a clock hand in a circle moves on a surface the amplitude result is a sine wave (Figure 3.7).

Wave theory describes a water wave as a sine wave vibration caused by the forces of gravity and elasticity acting at right angles to the water surface. When a wave arrives, a surface water molecule is pushed say up until gravity pulls it back down, then

Figure 3.7. A sine wave is a moving rotation

the water elasticity pushes it back up, etc. The wave just moves water molecules up and down hence a cork just bobs up and down as the wave passes. What “travels” on the surface is a transverse oscillation not the water itself.

Using imaginary wave mathematics, we can describe a light wave in the same way except that no one has any idea what is going up and down. We say it is the electromagnetic field but to name a cause is not to explain it. In quantum realism, light is a vibration into a quantum space that contains our space as a surface.