Section 3 d) Specification

3.14 understand that light waves are transverse waves which can be reflected,
refracted and diffracted

Light waves (electromagnetic waves) are transverse, meaning they oscillate perpendicular to the direction of travel. They are able to be reflected off of shiny surfaces at the same angle that they hit the surface with, refracted by the angles when changing from one medium to another (e.g. glass and air) slowing different parts of the light and causing it to bend, and diffracted by spreading out after passing a barrier.

3.15 use the law of reflection (the angle of incidence equals the angle of
reflection)

When you look into a plane mirror, the image is not distorted, it shows it as it is. This is because the angle does not change when light is reflected. It hits the mirror at one angle, and it will reflect at the same angle, about the normal.

This is easily remembered: i = r

3.16 construct ray diagrams to illustrate the formation of a virtual image in a
plane mirror

A virtual image can be created using a phenomenon called Pepper's Ghost. The ray diagram below provides explanation.

Another example of virtual imagery is placing two candles  equidistance from glass, so they are symmetrical, then lighting the one in front of the glass. The light will be reflected by the glass, and the candle behind will also appear to be lit.

3.17 describe experiments to investigate the refraction of light, using rectangular
blocks, semicircular blocks and triangular prisms

1. Place a glass or clear plastic rectangular prism on a sheet of paper and outline with pencil.
2. Decide the point at which you will shine the light in, and draw a perpendicular line - the normal. Draw other lines at different angles (ever 10 degrees) using a protractor.
3. Shine a light into the block at the normal, and mark two Xs on the emergent line. Repeat this with all of the angles you marked.
4. Connect the Xs, then connect them up to the original to create the light paths. Do the same thing for different types of blocks (semicircular prisms, triangular prisms, etc. )

Using a coloured light, maybe red or blue, would be easier than using white light because white light is made up of all different coloured light and so may split into a rainbow and be difficult to measure.

3.18 know and use the relationship between refractive index, angle of incidence
and angle of refraction:
n= sin i / sin r

This relationship is important to know, and will likely be asked for you to recall.
refractive index = sin (angle of incidence) / sin (angle of refraction)

3.19 describe an experiment to determine the refractive index of glass, using a
glass block

Shine a light through a glass block at different angles, with an interval of 10 degrees. Mark the emergent line, then connect back to the original line. Measure the angle of incidence, and use sin(i) / sin(r) to find the refractive index of each of the angles you measured, then find an average of them to get a more accurate result.

3.20 describe the role of total internal reflection in transmitting information along
optical fibres and in prisms

Total internal reflection allows light to be reflected inside a medium, so the information can be transmitted long distances, it is essentially trapped in there, because it is constantly reflected at an angle larger than its critical angle.

3.21 explain the meaning of critical angle c

The critical angle is the angle at which the light is neither reflected or refracted; any bigger and it will be totally reflected, any smaller and it will be refracted.

3.22 know and use the relationship between critical angle and refractive index:
sin c = 1 / n

This is another really important formula to know, and again will probably come up in the exam.
sin (critical angle) = 1 / refractive index

3.23 understand the difference between analogue and digital signals

Analogue signals are continuous, they have constantly varying frequencies and amplitudes.

Digital signals have two settings only: 1 and 0

3.24 describe the advantages of using digital signals rather than analogue signals

Analogue signals are easily distorted or altered, and are difficult or impossible to restore to their original state. Digital signals are more easily restored if distorted because they only have two settings.

3.25 describe how digital signals can carry more information

Digital signals have a larger bandwidth than analogue signals, meaning more information can be carried at once.

3.26 understand that sound waves are longitudinal waves and how they can be reflected, refracted and diffracted

Sound waves are longitudinal, they oscillate parallel to the direction of travel. Similarly to transverse electromagnetic waves, they can be reflected, refracted and diffracted.

3.27 understand that the frequency range for human hearing is 20 Hz – 20,000 Hz

Humans can only hear a small range of frequencies, between 20 and 20 thousand hertz .

3.28 describe an experiment to measure the speed of sound in air

1. Measure the distance between where you're standing and a large flat wall. 
2. Using clapping blocks, make a noise, then make another every time you hear an echo.
3. Once you are clapping at a steady rhythm, use a stopwatch to time how long 10 time intervals are (count 11 claps)
4. Use this to calculate how long it is for 1 clap (divide by 10), then divide the distance by the time for one clap. (if the distance from you to the wall is 100 m, use 200 m because the vibration needs to travel there and back)
5. The result should be around 343 m/s

3.29 understand how an oscilloscope and microphone can be used to display a sound wave

A microphone can be connected to a cathode ray oscilloscope, and used to detect the sound. The oscilloscope will begin tracing the pattern of frequency and amplitude and display it as a wave or a straight line.

3.30 describe an experiment using an oscilloscope to determine the frequency of a sound wave

Make a noise into a microphone connected to an oscilloscope. It will make a trace, which you can count the number of divisions for one oscillation. You can also adjust the time base to get more workable numbers. For example, if one division is 5 milliseconds, and one oscillation is 4 divisions, we know that it is 20 milliseconds per oscillation, or 0.02 seconds.
f = 1 / t
so f = 1 / 0.02
f = 50 Hz

3.31 relate the pitch of a sound to the frequency of vibration of the source

High pitched sounds have a high frequency, low pitched sounds have a low frequency.

3.32 relate the loudness of a sound to the amplitude of vibration.

The larger the amplitude, the louder the sound will be.