Rainbows
Waves
The white light spectrum
1. White light is a mixture of different colours of light.
2. Newton used a glass prism to separate the colours.
3. He identified 7 different colours.
4. Initials ROYGBIV
Waves
The white light spectrum
Violet is refracted more than red
The prism refracts the light
Light Wavelengths
Waves
The electromagnetic spectrum
Waves
Electromagnetic waves
1. Light is a transverse wave
2. It is one part of a much bigger family
3. This family is called
electromagnetic waves
Waves
Electromagnetic waves – common features
1. Transverse
2. Can travel through empty space
3. Speed in empty space
300 000000m/s (186 000 miles per second – not hour)
4. Can be reflected, refracted, diffracted.
Waves
Electromagnetic waves – differences
Each part is made of waves with different
1. frequencies and
2. wavelengths
Waves
Electromagnetic waves – parts
1. Radio/tv
2. Microwaves
3. Infra-red
4. Visible light
5. Ultraviolet
6. X-rays
7. Gamma - rays
Long waves
Low frequency
Short waves
High frequency
Waves
Electromagnetic waves – parts
1. Radio/tv
2. Microwaves
3. Infra-red
4. Visible light
5. Ultraviolet
6. X-rays
7. Gamma - rays
Waves
Electromagnetic waves – parts
Waves
Radio-TV waves
• Used to transmit radio and TV programmes
Waves
Radio-TV waves
• Long waves reflected by the ionosphere and can travel long distances
ionosphere
Waves
Microwave radiation - 1
• Used for transmitting information to satellites
Waves
Microwave radiation - 2
• Mobile phones transmit and receive microwaves
Waves
Microwave radiation - 3
1. Microwaves are absorbed by water making it hot
2. they can penetrate and cook food with a water content.
Action of microwaves
Waves
Infra red radiation - 1
• Can be detected by the skin as heat.
• Emitted by all ‘hot’ objects
Waves
Infra red radiation - 2
1. Used for cooking in grills and toasters
2. Used for heating in radiant type heaters
Waves
Infra red radiation - 3
• TV remote controls emit infra red
Waves
Infra red radiation - 4
• Passive infra red detector used for alarm systems
Waves
Visible light
• Used for seeing – the eyes detect light
Waves
Visible light
• Cameras detect light
Waves
Visible light
• Air, water, glass etc let light pass through them. They are transparent.
Waves
Ultra violet radiation - 1
• Fluorescent tube light produce uv inside the tube
Waves
Ultra violet radiation - 2
• Sun beds contain uv lamps
Waves
Ultra violet radiation - 3
• UV is used in security coding – special inks glow under UV.
Waves
X-radiation (rays) - 1
1. X-rays can travel through skin, muscle or flesh.
2. X-rays cannot travel through bone or metal
3. They are used to produce shadow pictures of bones and metal
X ray cat pin
Waves
X-radiation (rays) - 2
Waves
Gamma radiation (rays) -1
• Gamma rays can kill harmful bacteria in food.
Waves
Gamma radiation (rays) - 2
• Gammas are used to sterilise surgical equipment
Waves
Gamma radiation (rays) - 3• Gamma rays are used in medicine to kill
cancer cells
Stars emit em waves
Stars emit all types of em waves
1. we see the visible
2. Feel the IR
3. May be damaged by the UV
4. Astronomers ‘look’ at all the parts
Waves
The effect on living cells of microwaves
1. Absorbed by the water in cells
2. The cells can be damaged or killed by the heat
Waves
The effect on living cells of infra red
1. Absorbed by skin
2. Felt as heat
3. Can cause burns
Waves
The effect on living cells of ultra violet
1. Can pass through skin to deeper tissues.
2. Absorbed more by darker skin
3. High doses can kill normal cells
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
Waves
Ionising radiation
• Gamma and X radiation are ionising and must be treated with caution.
• They can be both useful and dangerous.