What are carrier waves?
Wves usd to carry any type of signal
What are radio and microwave spectrum divided into?
Why are different bands used for different communication purposes?
Shorter the wavelength of the waves:
- more information they carry
- shorter their range
- less they spread out
What are microwaves used for?
Satellite phone and TV signals - because they can travel between satellites in space and Earth
Why is it hard to say this is true?
Scientists think the radiation from mobile phones may affect brain , especially in children?
Further research is needed to evaulte this claim
optical fibres carrying visible light / infrared radiation are useful in communications?
Because they carry much more information than radio wave and microwave transmissions
Why is light not better at communications than optical fibres?
As light has much shorter wavelength than radiowaves/ microwaves
more secure because waves stay in fibre
Instructions using radio waves
- Microphone produced audio signal - sound waves reach
- Radio waves are asborbed by reciever aerial
- Reciever circuit separates the audio signal from carrier waves
- Audio signal is supplied to loudspeaker , to emit sound waves
What is audio signal's function?
Used to modulate (vary the frequency) of carrier waves
Modulated carrier waves are supplied to transmitter aerial , emits radio waves and carry this signal
What happens when radio waves are absorbed by the reciever aerial?
Induce an alternating current , causes oscilliations in reciever
Same frequency of the radio waves