waves - use of EM waves Flashcards
what are radio waves used for?
transmitting radio and terrestrial tv signals (received using an aerial)
why are radio waves used?
they can travel long distances before being absorbed eg by buildings and trees
what can longer wavelength radio waves do?
spread out between hills (diffraction)
what can radio waves reflect off? what does this allow us to do?
a layer of charged particles in the atmosphere (ionosphere) which allows us to send radio waves very long distances around the Earth
what are microwaves used for? why?
heating food as most food contain water molecules which absorb energy of microwaves. the energy causes temperature of food to increase
what are mircowaves used to communicate with? why?
satellites in space as microwaves can pass through earth’s atmosphere without being reflected or refracted
what is infrared emitted by? used by?
electrical heaters and also used to cook food in ovens
why is infrared used?
energy of infrared is easily absorbed by the surface of objects
what is the infrared from a heater absorbed by?
objects in the room making room warmer
infrared is also used in ________ _______
infrared cameras
e.g to check buildings for heat losses
important use of visible light?
communication using fibre optics
what are optical fibres?
very thin strands of glass
what can be transmitted down optical fibres?
pulses of light and these pulses of light can carry information
what are optical fibres used for?
carrying telephone and cable TV signals
Because visible light has a short wavelength……
it can carry a great deal of information
