Wave bye-bye to your sanity…

Paradoxes are fun – if you understand them. Watching others attempt to reconcile the conflict between the irreconcilable is amusing. For example:

The following sentence is false.

The previous statement is true.

Which of these statements are correct? If your head is beginning to hurt, then you had better go and buy a very large box of panadol, because you are going to need it during the next unit of work. We are beginning your investigation into the properties of light, and it only gets weirder (and more paradoxical) the further in you get. The truth of the matter is that physicists don’t really know (absolutely) what light is. Scientists rely on a set of models (models are ways to explain why light behaves the way it does), but the porblem is that light doesn’t play nice. Certain models explain some behaviours, but not others. In fact, no one model explains all of the properties of light. Over the course of the next unit, we will look at two models:

1. Ray Model
2. Wave Model

The Ray Model is the simplest, but we still use it for the simplicity in explaining things like reflection and refraction. I have previously written a post about this on this blog, here. However, in order to explain some more complicated phenomena, we need to use the Wave Model, which is the topic of this post. (in year 12, you will study the particle model, and for those of you with a masochistic streak (You know who you are…), check this out as an introduction to the Quantum Electrodynamic Model (what the bleep!) (ps. don’t watch the rest of this “documentary” – it is a pile of conspiracy-minded bovine excrement encrusted with credulous delusional pseudoscience).

A wave is defined as followes:

Wave: an periodical (regular) oscillation (disturbance) which travels through a medium, transferring energy from one location to another.

This means that a (physical/mechanical) wave is exactly what you think of when you see an ocean wave – a “bump” (this is the wave crest) in the water  (this is the medium) that travels in a direction, and gives energy to what it hits. Physical waves (i.e. waves that causes visible “bumps” in what they travel through) come in two main types: Transeverse and Longitudinal (there are more, but that will do for today (ok, if interested, you can start with torsional, shear and surface)). Transverse waves have the bump (“pulse”) perpendicular to the directions of travel (propagation), like this:

Longitudinal waves have their pulses parallel to the direction of propagation, like this:

This is summarised in the following video:

A pair of powerpoints that provide good information:

OK, now some sources of good supplementary information:

1. Classroom Physics: A great, detailed website. This should be your first site to visit! (link)
2. Zonaland: This is also good; not so pretty, but very well organised. (link)
3. Educational Electronics: This is OK, but focusses more on sound. (link)
4. Antonine Education: This is also good, but goes a bit further than we do this year (link)
5. Science-Class: some good stuff here too, but a bit simple. (link)

OK, and for the studious amongst you, remember that you must have finished the “What is Colour” task that was assigned last term. This worksheet has to be completed by Lesson 1, Week 2 so get cracking!

See you in Class!

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