• that a wave transports energy from one place to another
• that mechanical waves use particles to transfer energy (neighbouring particles bump into each other and set their neighbours moving). Eg. sound waves use air particles so it cannot travel through a vacuum (a vacuum is empty space with no particles in it at all!). Sound travels faster through solids than liquids than gases because the particles are more closely packed.
• that electromagnetic waves don't use particles (in fact particles interrupt their progress through a material) and can therefore travel through a vacuum. e.g. light
• that a point disturbance creates circular waves as the energy emanates in all directions

(Not my illustration - click on it to check out the site it is from!)

• distance, displacement, wavelength, amplitude - all measured in metres (m)
• frequency measured in hertz (Hz)
• time, period - measured in seconds (s)
• speed - measured in metres per second (m/s)

• speed = distance/time (v =s/t)
• wavespeed = frequency x wavelength(v = fl)

• The vibrations in a longitudinal wave are parallel to the direction in which the energy is travelling. Eg. sound.

• The vibrations in a transverse wave are perpendicular (at right angles) to the direction in which the energy is travelling. Eg. light.

Click here for an interactive program from Colorado University

• Wavelength (- lamda a Greek letter 'l') is the shortest distance between two particles that are oscillating in phase. (Distance between two crests on a displacement/distance graph). It is measured in metres (m)

• Period (T)is the time taken for one complete oscillation of a particle in the wave. (Distance between two crests on a displacement/time graph). It is measured in seconds (s).

• Amplitude (A) is the maximum displacement from the mean position. (To the top of a crest or bottom of a trough from the middle line in either graph).
• Frequency (f) is the number of oscillations per second. It cannot be read directly off a graph. You need to find (T) from the displacement/time graph and then find its reciprocal (f =1/T)

• Analogue signals contain all the information as a continuously varying wave
• Digital signals are a series of pulses - either high or low - on or off - sometimes expressed as binary code 1s and 0s.

See Analogue vs. Digital

You need to UNDERSTAND that:-

• An oscilloscope is a voltmeter that shows how electrical signals vary with time on a screen. It can show sound waveforms if a transducer such as a microphone is connected to it. This changes sound energy into electrical energy and shows the vibrations on the screen.
• In sound : high frequency means high pitch of note (lots of waveforms on the screen), low frequency (few waveforems) means low pitch of note (deep note).
• In light: high frequency means the blue end of the spectrum, low frequency means red and of the spectrum.
• In sound: big amplitude means loud note, small amplitude means quiet (not low as this can be used for pitch too) note.
• In light: big amplitude means bright light, small amplitude means dim light.
• to make high pitched sounds you use short, thin strings or short pipes and vice versa.
• to make loud notes you blow hard into wind instruments and pluck hard at string instruments.
• that sound travels much slower than light does.

For the examination you need to BE ABLE TO:-

Label wave diagrams :-