Tucked away at the end

Sometimes classes never reach the more interesting parts of Physics.

The Advanced Placement exams start this week, which means our tutor is being pressed into service to cover the last few topics quickly.  The AP syllabus is set by a nationwide organization and is intended to be college-level in scope and depth, so it includes some items beyond what would otherwise be found in a High School Physics course.  In practice, few classes spend much time on the final topics, and some years our tutor never sees them at all.  This is unfortunate, because (we think) they are among the more interesting parts of the subject.

Electrical circuits form one of these topics.  The arcane drawings with their voltage-drops and current arrows take time to master, since the setting is entirely new and any familiar concepts appear in different forms.  And at this level no really interesting or practical circuits can be presented; only a few students ever see an oscillator.  And yet electrical devices and networks are ubiquitous.  There is something practical to be gained in mastering voltage, amperes and what actually happens when you plug something in.  Everyone works with electrical power.

Another topic is optics, the characteristics of simple lenses and mirrors.  (This is dear to the heart of our astronomer.)  There is something almost magical about how images can be formed and manipulated by pieces of glass, and the principles are evident any time one looks into a shop window or at the blue sky.  But it’s been years since our tutor had occasion to pull out his lens collection.

Either of these topics would be more interesting than inclined planes, that ubiquitous and numerous population found in the dense forests and broad savannas of textbooks.  And very few people actually make much use of them, important simple machines as they are.  So could we, maybe, teach some of the interesting stuff first?  Start with electricity or optics, say, or at least not leave them until the very end?

Reluctantly, we concede that electrical circuits are probably not something to start with.  They are confusing enough now; without a concept of energy or the behavior of electrical charges the topic could be completely opaque.  Rules for analyzing a resistor network could be memorized, but they would mean even less than they do now.  Physics students already have enough incomprehension on their formula sheets.

Optics, though, might be possible.  The basic rules of reflection and refraction were worked out without much input from Physics, and lenses of excellent quality were being produced before much of our present textbook material was invented.  So there is no need to cover forces, energy or electromagnetism before trotting out the lens equation.  Unfortunately, that means that optics would not be much direct help in teaching those topics, which really do need to be covered sometime.

We still think that lenses and mirrors should appear earlier in the Physics course.  They could stimulate some interest that now lies dormant.  At least, they could provide a break from inclined planes.