Exam tips…

I make these general suggestions without having looked at the exam in detail (and having made them already in class on Thursday).

  • Memorise the relevant equations. You will be provided with the standard HSC formulae sheet (check it out here). There are quite a few important ones missing, especially Snell’s law (refractive index version) and the useful expression of the inverse square law. For a summary of all equations you’ll need to know, look here.
  • Look carefully at calculations before doing them.  Do you need to do any conversions? (eg. kHz to Hz, kilometres to metres etc). Have you been given the angles from the normal? Write down the relevant equation before substituting your values in.
  • Answer the question.  If you are asked (for example) to give two similarities and one difference, then make sure you give two similarities and one difference. If you are asked to include a diagram then include a diagram.
  • Label your axes on graphs, include units whenever they exist, make sure you graph things the right way around – “A vs. B” means A is on the vertical axis.
  • Go over the syllabus – it won’t take very long.  Just scan through it and make sure you know what each point is talking about.  You can’t be examined on anything else.  Here is a copy of the syllabus.
  • Don’t leave anything blank If you get stuck, remember that there is a good chance you will know how to answer most of the questions, and that there is a good chance you know how to do most of the calculations.  Just think about it for a bit longer and don’t assume you can’t answer it.

Equation Summary (The World Communicates)

This document gives an overview of all equations covered in ‘The World Communicates’. Details of all quantities and units are included, as well as some relevant comments on each equation.  A successful student will be familiar with all of these equations.  Note that some of these are not included on the board of studies formulae sheet.

Equation Summary

Digital Communication

Bluetooth

Many raw measurements result in analog data.  For example, when a microphone measures the sound pressure level to create an electric wave, the signal is analog.  However, the majority transmission / storage of information is done digitally.  Anything saved, transmitted or processed using a computer, or stored of DVD, CD, flash media etc is done so in digital format.

The slides outline how an analog wave is converted into a digital wave, and mention some examples of digital communication (blu-ray, mobile phones, modems and hard drives).

Powerpoint slides

Total Internal Reflection

You notice that when light is travelling from a dense medium (higher refractive index) to a less dense medium (lower refractive index), the angle of refraction is always bigger than the angle of incidence.  In this situation it is possible to have an angle of refraction of 90°, where the light does not enter the second medium, but travels along the boundary.

If the angle of incidence is increased further, all of the light will be reflected back into the first medium.  This is called total internal reflection.  The slides introduce and outline total internal reflection, the critical angle, and it’s application in fibre optics.  Instructions for an investigation are also included.

Powerpoint slides

Refraction

If an electromagnetic wave travels from one medium into another medium, it will experience refraction if the two media have different refractive indices (ie. if the wave moves faster in one of them, then it will refract at the boundary).  The mathematical description of refraction is more complex than reflection, and is known as Snell’s Law.

Snell’s law can be expressed in terms of the velocity of light in each medium, or the refractive index of each medium.  These are equivalent (you can easily convince yourself of this using the definition of refractive index).

The slides outline Snell’s law and include some calculations based on Snell’s law.  Follow this link for an excellent animated gif file of refraction.

Powerpoint slides

Refraction of light

Refractive Index

Although the speed of light (and other electromagnetic waves) is constant in a vacuum, it changes in other media. It is faster in air than in water for example.  It is convenient to define the refractive index as a ratio of the speed of light (c) to the speed of light in the particular medium.  The refractive index is a useful quantity in refraction calculations, and it is important to understand how it is defined.

These slides briefly introduce refractive index and some common values of refractive index.  Questions are also provided.

Powerpoint slides

Reflection

Infinite reflection

Reflection is not just a property of light, but of all electromagnetic waves, given a suitable reflective surface.  The angle at which light reflects from a surface is equal to the angle at which it strikes the surface (angle of incidence).  These angles are measured from the normal to the surface.  Reflection is widely used in our society.

These slides outline the law of reflection and a number of applications for different surfaces (concave, convex, plane, ionosphere, fibre optic cables).

Powerpoint slides