1. Rainbows

2. Waves The white light spectrum
White light is a mixture of different colours of light.
Newton used a glass prism to separate the colours.
He identified 7 different colours.
Initials ROYGBIV

3. Waves The white light spectrum
The prism refracts the light
Violet is refracted more than red

4. Light Wavelengths

5. The electromagnetic spectrum
Waves
The electromagnetic spectrum

6. Waves Electromagnetic waves
Light is a transverse wave
It is one part of a much bigger family
This family is called electromagnetic waves

7. Waves Electromagnetic waves – common features
Transverse
Can travel through empty space
Speed in empty space
m/s ( miles per second – not hour)
Can be reflected, refracted, diffracted.

8. Waves Electromagnetic waves – differences
Each part is made of waves with different
frequencies and
wavelengths

9. Waves Electromagnetic waves – parts
Long waves
Low frequency
Radio/tv
Microwaves
Infra-red
Visible light
Ultraviolet
X-rays
Gamma - rays
Short waves
High frequency

10. Waves Electromagnetic waves – parts
Radio/tv
Microwaves
Infra-red
Visible light
Ultraviolet
X-rays
Gamma - rays

11. Waves Electromagnetic waves – parts

12. Used to transmit radio and TV programmes
Waves Radio-TV waves
Used to transmit radio and TV programmes

13. Waves Radio-TV waves
Long waves reflected by the ionosphere and can travel long distances
ionosphere

14. Waves Microwave radiation - 1
Used for transmitting information to satellites

15. Waves Microwave radiation - 2
Mobile phones transmit and receive microwaves

16. Waves Microwave radiation - 3
Microwaves are absorbed by water making it hot
they can penetrate and cook food with a water content.

17. Action of microwaves

18. Waves Infra red radiation - 1
Can be detected by the skin as heat.
Emitted by all ‘hot’ objects

19. Waves Infra red radiation - 2
Used for cooking in grills and toasters
Used for heating in radiant type heaters

20. Waves Infra red radiation - 3
TV remote controls emit infra red

21. Waves Infra red radiation - 4
Passive infra red detector used for alarm systems

22. Used for seeing – the eyes detect light
Waves Visible light
Used for seeing – the eyes detect light

23. Waves Visible light
Cameras detect light

24. Waves Visible light
Air, water, glass etc let light pass through them. They are transparent.

25. Waves Ultra violet radiation - 1
Fluorescent tube light produce uv inside the tube

26. Waves Ultra violet radiation - 2
Sun beds contain uv lamps

27. Waves Ultra violet radiation - 3
UV is used in security coding – special inks glow under UV.

28. Waves X-radiation (rays) - 1
X-rays can travel through skin, muscle or flesh.
X-rays cannot travel through bone or metal
They are used to produce shadow pictures of bones and metal

29. X ray cat pin

30. Waves X-radiation (rays) - 2

31. Waves Gamma radiation (rays) -1
Gamma rays can kill harmful bacteria in food.

32. Waves Gamma radiation (rays) - 2
Gammas are used to sterilise surgical equipment

33. Waves Gamma radiation (rays) - 3
Gamma rays are used in medicine to kill cancer cells

34. Stars emit em waves Stars emit all types of em waves
we see the visible
Feel the IR
May be damaged by the UV
Astronomers ‘look’ at all the parts

35. Waves The effect on living cells of microwaves
Absorbed by the water in cells
The cells can be damaged or killed by the heat

36. Waves The effect on living cells of infra red
Absorbed by skin
Felt as heat
Can cause burns

37. Waves The effect on living cells of ultra violet
Can pass through skin to deeper tissues.
Absorbed more by darker skin
High doses can kill normal cells

38. Waves The effect on living cells of X –rays and gamma rays
Can pass through soft tissues
Some is absorbed by the cells
High doses can kill normal cells
Low doses can cause normal cells to mutate and become cancerous

39. Waves Ionising radiation
Gamma and X radiation are ionising and must be treated with caution.
They can be both useful and dangerous.