Ultra-violet
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Contents
Key Stage 4
Meaning
Ultra-violet are the third highest frequency and third shortest wavelength electromagnetic waves.
About Ultra-violet
- Ultra-violet is a transverse waves.
- Ultra-violet can travel through a vacuum as well as through gases in the Earth's atmosphere.
- The speed of ultra-violet through a vacuum is 300,000,000m/s.
As a wave ultra-violets can be:
- Transmitted - ultra-violets can pass through a medium.
- Absorbed - The energy transferred by ultra-violet can be taken in by certain materials, particularly dark coloured materials.
- Reflected - Ultra-violet can bounce off an interface between two media, particularly the surface of a shiny metal.
- Refracted - Ultra-violet can change direction when they cross the interface between two media.
Unique Properties
- Ultra-violet can cause electrons in some materials to gain enough energy to leave atoms creating ions which can destroy chemical bonds.
- Ultra-violet does not penetrate through the skin.
- Ultra-violet is scattered by the Earth's atmosphere.
Applications
- Ultra-violet can cause electrons in the atoms of fluorescent molecules to gain energy. When the electrons lose this energy they emit visible light. This can be used to reveal fluorescent ink to detect forged bank notes
- Ultra-violet causes damage to the skin by breaking chemical bonds so in an effort to protect itself the skin produces melanin, a brown pigment. This causes the skin to become tanned. This is used in tanning beds.
- Ultra-violet can destroy micro-organisms in water by breaking chemical bonds in those micro-organisms, so can be used to sterilise water.
Dangers
- Ultra-violet can cause sunburn and skin cancer by ionising and damaging DNA molecules in the skin cells leading to a mutation.