Topic 3 - Uses of EM Waves Flashcards
what are radio waves?
EM radiation with wavelengths longer than 10cm
why can long-wave(1-10km) radio be transmitted a long way?
long wavelengths are bent around the curved surface of the earth
why can shortwave (10m-100m) radio be transmitted a long way?
they are reflected from the ionosphere
why cant radio waves used for TV/FM broadcasting only be received when you’re in direct sight of the transmitter?
they have very short wavelengths (10cm-10m), so the signal doesn’t bend around hills
what are microwaves?
EM waves with a wavelength of around (1-10cm)
how are microwaves used for communication?
They are used for satellite communication and for mobile phone calls
how does satellite TV work with microwaves?
the signal from a transmitter is transmitted into space, picked up by a satellite receiver which transmits the signal back to Earth where a satellite dish on the ground receives it
how are microwaves used for cooking?
microwaves are absorbed by water molecules in the food and are then conducted/convected to other parts
what are uses for IR radiation?
electrical heaters and grills
what gives out IR radiation?
everything
how is visible light used for communication?
optical fibres
how do optical fibres work?
bouncing waves off the sides of a very narrow core
how does photography work?
cameras use a lens to focus visible light onto a light-sensitive film
how do fluorescent lights work?
they use UV radiation to emit visible light
what are x-rays used for?
viewing the internal structure of objects and materials
