How light came to be thought of as consisting of electric and magnetic fields, and the history of the strange relationship between electric and magnetic fields.
Light is made up of magnetic fields and electric fields, intertwined — at least from a certain point of view. While every child knows what a magnetic field is, sort of, less know what an electric field is, even though they are just as easy to demonstrate. We’ll look at electric fields in this tutorial.
Since light is, from a certain point of view, made up of electric and magnetic fields, it behoves us to study them a little. This is a tutorial on the history and mysterious nature of magnetic fields. Next time we’ll look at electric fields, before putting the two together.
Stuff that moves has energy by virtue of the fact that it’s moving. Although it’s hard to say what energy really is, we know it when we see it, and movement definitely counts. In this tutorial we’ll do a little bit of algebra to get from our basic definition of energy to figuring out how much energy a moving thing has, exactly. This is really going to help a lot when we get on to looking at light and photons. Honest.
Before we start looking at light, let’s break down some of the key concepts involved in understanding light. We’ll start here with energy; a term that is rigorously defined in physics and yet nevertheless impossible to fully grasp. In fact, it’s surprising how many things in physics, or indeed in life, are possible to define and yet impossible to grasp. At least being able to define a thing is better than bandying about words without having any clear agreed definition — we’ll leave that to philosophers. At least for now.
Photos are weird. Fact. Once we start thinking that light is made up of photons, we’re left with some pretty strange conundrums just as soon as we start to think it through. It’s almost enough to make you give up and start arguing that photons don’t exist …. except that they’re so darned useful. By considering the weird nature of polarized photons, we can start to see what kind of mathematical theorem we might be looking for exactly, when we’re trying to formulate a mechanics of the quantum realm.
A tutorial on polarized light. Polarized light behaves according to rules that we could think of as belong to classical physics. Nothing too weird happens, and we can make concrete predictions about future observations on the same ray of light. But don’t worry, things are going to get very crazy when we start to look at photos in the next tutorial. This tutorial just paves the way for the vile monstrous insanity that is to follow.
A tutorial on observables and compatibility, using some examples drawn from every day life.
When we’re looking at very small objects, we can’t observe them without disturbing them. The process of measuring the value of a property that we consider them to have, becomes an active process that causes them to manifest that property — a bit like measuring how violent a person is by punching him in the face and seeing if he attacks you or not. One side effect of this is that often measuring one “observable” will disturb the measurement of another observable, in which case we say the two observables are incompatible.