Rainbows

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

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

Light Wavelengths

The electromagnetic spectrum Waves The electromagnetic spectrum

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

Waves Electromagnetic waves – common features Transverse Can travel through empty space Speed in empty space 300 000000m/s (186 000 miles per second – not hour) Can be reflected, refracted, diffracted.

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

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

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

Waves Electromagnetic waves – parts

Used to transmit radio and TV programmes 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 Microwaves are absorbed by water making it hot 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 Used for cooking in grills and toasters 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

Used for seeing – the eyes detect light 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 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

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 we see the visible Feel the IR May be damaged by the UV Astronomers ‘look’ at all the parts

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

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

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

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.