# 3 Waves – Part B “Properties of Waves”

### Syllabus Aims…

3.3 know the definitions of amplitude, wavefront, frequency, wavelength and period of a wave

3.4 know that waves transfer energy and information without transferring matter

3.5 know and use the relationship between the speed, frequency and wavelength of a wave:

wave speed = frequency × wavelength

v = f × λ

3.6 use the relationship between frequency and time period: frequency = 1/time period

f = 1/T

3.7 use the above relationships in different contexts including sound waves and electromagnetic waves

3.2 explain the difference between longitudinal and transverse waves

3.9 explain that all waves can be reflected and refracted.

3.8 explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer, and that this is known as the Doppler effect  (May be covered in Y10)

### Video Resources…

Wave Properties: This video explains the basic idea of a “waveform” and ripple tank to show “displacement” or amplitude over a period of time “T” with equations…

Period / Frequency: This video shows you how to do calculations for waves…

Longitudinal & Transverse: A super clear explanation of all the basic labels for wave and T and T waves.

String Waves: This is the required GCSE practical for AQA which is a way to work out the Speed of a wave on a string.

Doppler Shift: Example how how it sounds!

Doppler Shift: This shows now it works with compression or expansion of wave forms or a shift in wavelength

## One Hertz Water Wave in a Kefalonia Swimming Pool

In Physics it is often quite useful to get back to basics and think about what does frequency really mean.

Often students struggle with the concept but it actually really simple. ...
It means how many cycles there are in a wave or oscillation per second.

Just like a wheel spinning, how many times per second does it go around?

1Hz is one per second or 1/s
2Hz is two per second or 2/s

2Hz is clearly more cycles in a time of 1s so the wave takes 0.5s for each time period.

20Hz is 20 per second so 0.05s = the time period.

The unit is also strange as its per second and instead of writing /s we came up with the unit of Hertz from the Physics professor who found it out.