Electromagnetic waves

• electromagnetic waves are transverse waves that transfer energy from a source to an absorber
• electromagnetic waves travel at 300,000,000m/s (the speed of light)
• electromagnetic waves do not require a medium to travel
• shorter wavelength = higher frequency and higher energy
• gamma rays have the shortest wavelength and highest frequency
• the order of electromagnetic waves is; radio waves, microwaves, infra-red waves, visible waves, ultraviolet, x-ray, and gamma ray
• radio waves can be used to transmit information over long distances without cables or wires
• radio waves can be reflected by the ionosphere
• radio waves are used for radio stations (long wavelengths) and terrestrial TV (short wavelengths)
• diffraction is the ability long wavelength radio waves have to bend around obstacles
• mobile phones send and receive signals from nearby mobile towers using radio frequency waves (a form of electromagnetic energy between radio and microwaves)
• microwaves can pass through the ionosphere to communicate with satellites
• microwaves are used for satellite TV and microwave ovens
• infra-red waves are heat waves emitted mainly by the sun
• infra-red waves are used for thermal imaging
• visible light is the light that can be seen by the naked eye
• the visible light is; red, orange, yellow, green, blue, indigo, and violet
• an example of visible light is fibre optic cables
• ultraviolet light cannot be seen however we know it is there because it gives us sun tan/burn
• most ultraviolet rays are blocked by the ozone
• ultraviolet triggers vitamin D and melanin production
• sunscreen absorbs UV to protect the skin
• ultraviolet is used for tanning beds and flourescence
• x-rays are short penetrating waves that pass through the skin and muscle but are absorbed by the bone
• radiographers wear protective vests to prevent exposure to radiation
• x-rays are used in hospitals and airport security
• gamma rays can cause DNA in our cells to change causing cancer