The Electromagnetic Spectrum

Hold your hand in front of a television remote control and press a button. Nothing happens. Point the remote at the television across a dark room and the channel changes instantly, with no wire, no sound and nothing at all for your eyes to see. Something crossed that room, carried energy from the little diode in the remote to the sensor on the television, and did it at three hundred million metres every second. It was the same kind of thing that lets you see this page, the same kind of thing that cooks a potato in a microwave oven, the same kind of thing that photographs the bone in a broken wrist. One family, one speed, one continuous spread of possibilities.

This lesson takes that family apart and puts it back in order. You will learn the sequence of the seven regions and what actually changes as you walk along it, why the strip your eyes can detect is such a thin slice of the whole and why different wavelengths inside it look like different colours, which regions carry our phone calls and our television and why each of them was chosen, what every region is used for beyond communication, and where along the sequence radiation stops merely warming you and starts tearing electrons off your molecules. By the end you should be able to take a wavelength you have never met before, put it in its place on the line, and say what it is used for and what it would do to you.