Presentation on theme: "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."— Presentation transcript:
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
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 m/s ( 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 Ultra violet radiation - 3 UV is used in security coding – special inks glow under UV.
Waves X-radiation (rays) 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.