1. Unit G9
Waves

2. Lesson 1
What are waves?

3. Aims Describe waves and their properties
Understand the words crest, trough, longitudinal, transverse, amplitude, and wavelength
Give some examples

4. Mexican & Slinky Demos

5. Copy notes Waves are vibrations that travel from one place to another
The material that vibrates stays in its place, only the vibration energy moves
There are two kinds of vibration:
in & out – called longitudinal
up & down – called transverse
Longitudinal waves travel parallel to the vibrations
Transverse waves travel perpendicular to the vibrations HT

6. Drawing
Draw two diagrams, one showing a longitudinal wave the other showing a transverse wave
See Milner page 118 for some examples

7. Wave Diagrams Look on p114 of Milner
Write a definition for amplitude and for wavelength
Include a diagram like this one …
wavelength
crest
amplitude
trough

8. Worksheet
Complete worksheet

9. Plenary – qwik qwiz
Sound is made by a speaker. The cone moves in & out. What kind of waves are sound waves?
The sound is made louder. The cone moves in & out further. What would be different about a drawing of the waves?
John can see ripples on a pond. There are 5 ripples in 1m. What is the wavelength?

10. Aims Describe waves and their properties
Understand the words crest, trough, longitudinal, transverse, amplitude, and wavelength
Give some examples

11. Lesson 2
The Wave Formula

12. Aims Understand the word ‘frequency’ Know and use the wave formula
Know how amplitude and frequency affect wave speed

13. Frequency/speed using slinky/rope
Demo
Frequency/speed using slinky/rope

14. Copy notes
Frequency is the number of vibrations that the source makes every second
It is measured in Hertz (Hz)
Speed tells us how quickly the energy goes from one place to another
It is measured as usual in m/s

15. Formula
If 5 waves are made every second and each wave is 2m long, that makes ___ m of wave per second
So if frequency=5Hz and wavelength=2m the speed is 10m/s
So the formula must be …
Speed (m/s) = Frequency (Hz) x Wavelength (m)

16. Wave Formula Practice
Complete worksheet

17. Practical Follow instructions on practical sheet
You clear up any mess before leaving!

18. Aims Understand the word ‘frequency’ Know and use the wave formula
Know how amplitude and frequency affect wave speed

19. Lesson 3
Water, sound and light

20. Aims Describe in detail how refraction happens
Draw and interpret ray and wavefront diagrams of reflection and refraction
Describe situations where water waves, light and sound can all be reflected and refracted

21. Revision – Reflection Light travels in straight lines
It bounces off objects – this is called reflection
If the object is flat and smooth the incoming and outgoing angles are the same
Draw red book p36 bottom

22. Revision – Refraction
Light changes direction if it goes into another material such as glass or water
It changes direction because it changes speed
normal line

23. Year 8 Revision Set 3 and Set 2 (F) only Work through Milner p110-111
Do all questions

24. Wavefront diagrams - copy notes
A wavefront diagram is a birds-eye view, showing the crests of the waves
The spacing is the wavelength
The waves are moving at right angles to the wavefronts
Draw the wavefront diagram showing water waves reflecting off a wall – mark the wavelength in a different colour

25. Refraction
Refraction happens because the waves change speed in the new material
This makes the waves bunch up as well as change direction
The wavelength gets shorter because the waves slow down
(beach.mov)
(refr_anim.dir)

26. Copy diagram

27. Do light & sound work like water waves or like particles?
Complete the table together:
Light
Sound
Snooker balls
Water waves
Bounces off things (reflects)
Changes direction if it slows down (refracts)
So refraction suggests light and sound are like waves, not balls

28. Aims Describe in detail how refraction happens
Draw and interpret ray and wavefront diagrams of reflection and refraction
Describe situations where water waves, light and sound can all be reflected and refracted

29. Homework Do the questions from the sheet Full answers in your book
All drawings pencil and ruler or you will have to do them again

30. The Electromagnetic Spectrum
Lesson 4
The Electromagnetic Spectrum

31. Aims List the regions of the electromagnetic spectrum in order
Know how these waves are different from sound and water waves
Know how their speed, wavelength and frequency change

32. Demo
OHT spectrum

33. Copy notes Light waves can have different wavelengths
Short waves look blue to us
Long waves look red to us
R – longer waves O Y G B I
V – shorter waves

34. Copy notes
Light waves can be made with even longer or shorter wavelengths but we can’t see them
Light is one part of a family of electromagnetic waves
They all travel at the speed of light
They can pass through empty space (sound can’t)

35. Draw Draw out the electromagnetic spectrum
Put these words at the right ends:
long wavelength
short wavelength
high frequency
low frequency
Make up a mnemonic to remember
RMIVUXG

36. Practical
Carry out the instructions on the sheet

37. Practical Do these invisible waves really exist?
Take out your phone – yes, really!
Go to camera and select ‘night mode’
Your camera can now ‘see’ infra-red waves as well as light waves
To prove this, fire a remote control at your camera – you can’t see it flashing, but the camera can
Now draw and describe what you did

38. Aims List the regions of the electromagnetic spectrum in order
Know how these waves are different from sound and water waves
Know how their speed, wavelength and frequency change

39. Lesson 5
Uses of EM Waves #1

40. Aims Know what can happen when waves hit an object
Explain the uses of X-rays
Explain the uses of infra-red radiation
Know the advantage of optical fibres

41. Copy notes When waves hit an object they are:
reflected,
absorbed or
transmitted.
Depending on the type of wave and material this can be useful

42. X-rays – copy and complete
X-rays are transmitted by soft materials but partly absorbed by denser materials
This makes them useful for looking inside the body, and for security scans at airports
X-rays pass through …
X-rays absorbed by …
When looking in the body …
When scanning bags …

43. Infra-red – copy and complete
Infra-red (IR) rays come from all warm objects
They are absorbed by the surface of most objects making them heat up
Low power IR can be used to send signals
Uses:
grills, house security sensors, remote controls, cable TV/telephone
For each use, write one sentence about how it works (see Milner p137)

44. Practical – SAFETY GOGGLES
Copy notes:
Light and infra-red waves can be used for sending messages down optical fibres (e.g. phone calls, cable TV)
This is better than using electric cables because there is very little loss of signal in the fibre
Now follow the practical sheet
VERY HOT OBJECTS &
BROKEN GLASS!
WORK SAFELY AT ALL TIMES

45. Aims Know what can happen when waves hit an object
Explain the uses of X-rays
Explain the uses of infra-red radiation
Know the advantage of optical fibres

46. Lesson 6
Uses of EM Waves #2

47. Aims Explain the uses of radio waves
Explain the uses of different wavelengths of microwaves

48. Radio – copy
Radio waves are very long (over 1m) and pass through most objects
They are used to send the information for TV and radio programmes
They are absorbed by metal aerials – they make the electrons in the metal vibrate (making an alternating current)

49. Microwaves – copy
Microwaves are shorter than radio waves – from a few mm up to 1m
Some wavelengths are absorbed by water and are used to heat food
Other wavelengths are used for signals e.g. satellite TV, mobile phones, Bluetooth, and wireless internet
Metals reflect microwaves e.g. satellite dish, grille inside microwave door

50. Questions Complete the question sheet
Use notes and Milner book to help you
Answer all basic questions
Questions marked * need some lateral thinking (**’s are very awkward!)
Go on to the (easier) summary sheet for uses of EM waves instead if you prefer

51. Homework
Next lesson you will need a pair of headphones like the ones used for an iPod or MP3

52. Aims Explain the uses of radio waves
Explain the uses of different wavelengths of microwaves

53. Lesson 7
Communications

54. Starter – recap Give three uses for microwaves
Which waves have the longest wavelength?
Which waves have the highest frequency?
Which waves can pass down optical fibres?
Which waves heat up materials that absorb them?
What happens when microwaves hit a metal object?
What happens when radio waves hit a metal object?

55. Aims Know what an analogue signal is
Explain how to make a wave carry information
Know the job of a receiver

56. Copy notes
Sound waves cannot travel very far before they lose strength (amplitude)
To broadcast sounds we make a radio wave that is like the original sound and transmit the radio wave
The radio signal is called analogue

57. Copy notes
Analogue radio signals can be like the original sound in two ways
An AM signal has an amplitude that is changed to be like the original sound
An FM signal has a frequency that is changed to be like the original sound
The receiver decodes the radio signal to get the original sound back

58. Animations Draw the AM animation – this one will be in the exam
(P1b swf files)

59. Building an AM receiver
This part of the circuit tunes-in to the
radio station you want to receive
This part of the circuit filters
out the radio signal to leave
the original sound

60. Aims Know what an analogue signal is
Explain how to make a wave carry information
Know the job of a receiver

61. Lesson 8
Digital Signals

62. Aims Know what a digital signal is
Explain how to convert analogue signals to digital codes and vice versa
Explain the advantages of digital signals

63. Copy notes/diagrams
Digital signals are signals that are either on or off
Analogue Digital

64. Converting analogue to digital
Step 1: Sampling the analogue signal
Step 2: Convert samples to 0’s and 1’s
Step 3: Transmit a long string of 0’s and 1’s
(P1b pulse code mod)

65. Digitising

66. Why bother? – copy notes As waves travel
they get weaker (lose amplitude)
interference (noise) gets added
When signals are boosted the noise gets worse as well
The signal quality gets worse and worse
(P1b a-to-d)

67. Copy
When a digital signal is boosted it can be cleaned-up at the same time
All the 0.1’s are turned back into 0’s
All the 1.1’s/0.9’s are turned back into 1’s
The signal quality remains perfect
Draw noisy analogue and digital signals from animation – explain why digital is better

68. Aims Know what a digital signal is
Explain how to convert analogue signals to digital codes and vice versa
Explain the advantages of digital signals

69. Homework
Transmitting signals sheet