1. KS4 Waves: Wave Character

2. Energy and Waves : Introduction
Waves carry energy from one place to another.
There are 2 main types of wave you need to know about:
Transverse Waves e.g. light waves
Longitudinal Waves e.g. sound waves

3. Waves : Introduction TRANSVERSE WAVES
Make a transverse wave using a rope between two people like this :
What type of energy is the wave transferring?
In which direction is the energy moving?
In which direction is each part of the rope moving? [put a marker on the rope to help you see]
kinetic

4. Waves : Introduction TRANSVERSE WAVES
You should have noticed that each part of the wave moves at right angles [90º] to the direction the energy is moving in:
Particle Movement
Energy Movement
Make a labelled diagram of your rope like this :

5.  a  a  Waves : Introduction TRANSVERSE WAVES Crest / Peak
 Displacement + 
Time a 
Trough

6. Wavelength and amplitude
What is the wavelength () of a transverse wave?
It is the distance between two consecutive points on the wave.
What is the amplitude (a) of a transverse wave?
It is the half-height of the wave, the bigger the amplitude of the wave, the more energy it has.

7. Animation to demonstrate wavelength, amplitude and frequency

8. Waves : Introduction LONGITUDINAL WAVES
Make a longitudinal wave using a spring between two people like this :
What type of energy is the wave transferring?
In which direction is the energy moving?
In which direction is each part of the spring moving? [put a marker on the spring to help you see]
kinetic

9. Waves : Introduction LONGITUDINAL WAVES
You should have noticed that each part of the wave moves in the same direction as the direction the energy is moving in:
particle movement
energy movement
When you speak to someone, the air vibrates as a longitudinal wave :

10.   Waves : Introduction LONGITUDINAL WAVES
Make a labelled diagram of your spring like this :
Compression
Compression
Rarefaction
Rarefaction  

11. Transverse or longitudinal?
light
sound
p-waves
water
s-waves
ultrasound
ultraviolet
light
ultrasound
sound
water
p-waves
s-waves
ultraviolet

12. Waves : Frequency
The number of waves passing a point each second is called FREQUENCY [ƒ]
Frequency [ƒ] is measured in hertz [Hz]
Frequency [ƒ] = Number of waves passed  Time [s]
1 wave per second = 1 Hz
If the wave below passes a point in 1 second, what is it’s frequency?

13. Waves : Frequency Wave Cycles Time (s) Freq (Hz) 2 6 3 10 5 1 0.5
Complete the table
Wave
Cycles
Time (s)
Freq (Hz) 2 6 3 10 5 1
0.5

14. Waves : wave speed
Imagine waves on the sea travelling over a shipwreck:
 = 2m
1 second later :

15. Waves : wave speed
In the diagram, 5 waves pass the shipwreck in 1 second………………….so the frequency = 5 Hz
The wavelength [] = 2 m
This means that the waves travel 10 m in 1 s
……….………………so the speed is 10 m/s
So, in this example, the
frequency X wavelength = speed
5 X = 10
Hz m m/s
This is usually written as :

16. V =  x   = V   and  = V   Waves : wave speed
For the Higher Tier papers, you will need to be able to change the subject of the formula :
 = V   and  = V  

17.   x v f Formula triangles
Formula triangles help you to rearrange formula. The triangle for the wave equation is shown below:
Whatever quantity you are trying to find cover it up and it will leave you with the calculation required.
…and you are left with the sum…
So if you were trying to find frequency, f…..
f = v  v  
…you would cover f up… f  x

18. Wave Speed – complete the table
3.0
0.2
1.32
2.4
0.01

19.  Energy and Waves : A Question
The photograph shows waves travelling across the surface of a pond. 1m 
1) Is this an example of a transverse or longitudinal wave?
2) Estimate the wavelength of the wave:
3) If the frequency of the wave is 0.2 Hz, calculate the speed of the wave:
transverse
0.15m
0.03m/s

20. Which wave below is a longitudinal wave?
Ultraviolet
Water
Light
Sound 

21. What are the units of frequency?
Metres
Hertz metres
Hertz/metres
Hertz 

22. A wave has a wavelength of 6m and a frequency of 5Hz
A wave has a wavelength of 6m and a frequency of 5Hz. What is the speed of the wave?
1.2 m/s
0.88 m/s
3.0 m/s
30 m/s 