Electromagnetic Spectrum
Cards (8)
- All EM waves are transverse waves
- All EM waves travel through a vacuum or air
- The frequency increases and decreases in wavelength going down the spectrum
- EM waves transfer energy from a source to an absorber
- A hot object transfered energy by emitting infrared radiation, which is absorbed by the surrounding air
- Radio waves are used for communication - wavelength longer than 10cm
- Long wave radios received far - long wavelength diffract around curved surfaces
- Short wave radios received long distances from transmitter - reflected from ionosphere
- Bluetooth uses short radio waves to send data over short distances
- Microwaves used by satellites - pass easily through atmosphere of water vapour
- Microwaves sent to satellite, satellite transmits signal back to Earth, received by satellite dish
- Microwaves used in cooking - absorbed by water molecules
- Microwaves penetrate few centimetres into food
- Absorbed and transfer energy to water molecules in food, heats up water
- Water molecules transfer energy to rest of molecules in food by heating - quickly cooks food
- Infrared radiation used in infrared cameras
- IR radiation detected and turned into electrical signal - hotter object, brighter colour
- Infrared radiation used in cooking food
- Temperature increases when absorbing IR radiation
- Infrared radiation used in electrical heating
- Wire with current heats up
- Wire emits IR radiation
- Radiation absorbed by objects and air of room
- Energy transferred to thermal energy stores, increase in temperature
- Visible light used in fibre optic communications
- Optic fibres carry data over long distances as visible light
- Light rays bounced back and forth until reached at end of fibre
- Ultraviolet is used in sun tanning
- Ultraviolet is used in fluorescent light
- Lights generate UV, remitted as visible light by layer of phospor
- Energy efficient
- X rays are used in photographs
- Pass easily through flesh but not easily through dense material