P13.2 Light, infrared, microwaves, and radio waves Flashcards
What is white light?
Light from ordinary lamps and from the Sun
What do optical fibres use?
Infrared radiation
Why do optical fibres use infrared radiation instead of visible light?
Because infrared radiation is absorbed less than visible light in the glass fibres
What are optical fibres?
Think glass or plasic fibres that can carry data
How do optical fibres work?
Light is reflected repeatedly and undergoes total internal reflection
Why are optical fibres used?
They cannot escape from the fibres
Makes them more secure than radio or microwaves
They can carry much more information as light has a much shorter wave length than micro or radio waves
What are some advantages of optical fibres?
Do not suffer from interference
Much faster than copper wires - as more information can be carried
Why do people use microwaves for communications?
Because microwaves can pass through the ionosphere and reach satellites above the earth
Microwaves can also carry mobile phone signals
Why are microwave ovens useful?
They heat food faster than normal ovens
This is because they can penetrate into the food and are absorbed by the water molecules in the food - heating it
The oven doesn’t absorb microwaves - since it doesn’t contain any water molecules
Therefore not becoming hot
What are radio waves used for?
Used to carry radio, Tv and mobile phone signals
What are the advantage of shorter wavelength waves?
Can carry more information
Spread out less
Shorter range
