Infra-red

Key Stage 4

Meaning

Infra-red are the third lowest frequency and third longest wavelength electromagnetic waves.

About Infra-red

Infra-red is a transverse waves.

Infra-red can travel through a vacuum as well as through gases in the Earth's atmosphere.

The speed of infra-red through a vacuum is 300,000,000m/s.

As a wave infra-reds can be:

• Transmitted - Infra-reds can pass through a medium.
• Absorbed - The energy transferred by infra-red can be taken in by certain materials, particularly dark coloured materials.
• Reflected - Infra-red can bounce off an interface between two media, particularly the surface of a shiny metal.
• Refracted - Infra-red can change direction when they cross the interface between two media.

Unique Properties

Infra-red can cause atoms and molecules to vibrate, heating a material.

Applications

Different frequencies of infra-red have different applications.

Infra-red is used in remote controls and night vision because it is invisible to the human eye but can be transmited through the air without being absorbed.

Infra-red can be used in thermal imaging because objects emit infra-red radiation due to their temperature. The higher the temperature the more infra-red they emit.

Infra-red can be used to cook food because it can cause atoms and molecules to vibrate, heating the food.

Infra-red can be used in fibre optic communication because it is not absorbed by the glass that the fibres are made from and it is reflected internally by the interface between the glass and the air.

Dangers

Infra-red can cause skin burns because it can cause atoms and molecules to vibrate, heating the material.

References

AQA

Infrared, pages 200, 206, 209, 210, GCSE Combined Science Trilogy; Physics, CGP, AQA

Infrared, pages 242, 248, 256-259, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA

Infrared; absorption, page 220, GCSE Physics; Student Book, Collins, AQA

Infrared; detector, pages 221, 233, GCSE Physics; Student Book, Collins, AQA

Infrared; emission, page 221, GCSE Physics; Student Book, Collins, AQA

Infrared; investigating, pages 209, 210, GCSE Combined Science Trilogy; Physics, CGP, AQA

Infrared; investigating, pages 257, 258, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA

Infrared; radiation, pages 191, 196-7, 213-14, 219-21, 230, 232-5, GCSE Physics; Student Book, Collins, AQA