Radio Waves and Microwaves

Radio Waves and Microwaves

phone mobile
radio waves and microwaves are very important to us for communication .

microwave
And for heating up left over pizza!

Electromagnetic

They are both on the long wavelength end of the electromagnetic spectrum :

images/em-spectrum.js

  • Radio waves have wavelengths of 1 m up.
    The frequency at 1 m is 300 MHz.
  • Microwaves have wavelengths of 1 mm (millimeter) to 1 m.
    The frequency at 1 mm is 300 GHz.

( eminence : some people say microwaves are equitable a type of radio wave, so for them radio waves have wavelengths of 1 mm up. )
We can create radio receiver and microwaves, and they are besides produced by the Sun and many other natural sources .

Wireless Communication

We use radio receiver and microwaves to communicate without wires. This is big, as we can move around and live our lives while hush being in touch .

Transmitting and Receiving

radio mobile phone
Transmit … and Receive on a device
radio waves are produced by a vibrating electric current in an antenna …
… the electromagnetic waves then spread out …
… and are then received by a small antenna inside your device, that detects the identical little measure of current created by the radio waves .
Your device can then decode the signal, and you can watch or listen to what was sent out .

Broadcasting

radio waves are adept at broad project ( sending out to lots of receivers ) and that is how we get to listen to radio and television broadcasts .
antenna tv
TVs ( and radios ! ) can receive broadcast signals using antennas .
radio waves are good at bending around buildings and hills by diffraction ( see below besides ) .

Microwave Ovens

Microwave ovens use electromagnetic waves at a frequency of 2.45 GHz (wavelength about 12 cm) that make body of water molecules vibrate fast and heat up .
microwave magnetron, stirrer and pie absorbs
Microwaves are created by the Magnetron,
are sent in different directions by the scaremonger,
bounce off alloy surfaces,
and are absorbed by the water in food .
Microwaves can travel through field glass and plastic and penetrate about a centimeter into food ( depending on the food ), but bounce off metal surfaces .
There must constantly be something to absorb the microwaves, such as food or a methamphetamine of body of water .
so basically you are cooking by heating up the water in the beginning curium or so of the food. That is why many recipes say to leave the food stand for a while ( to let the heat spread evenly ) .
Microwaves can besides heat us up and can damage our cells. Keep the door closed when on, and never use a damaged microwave oven .

diffraction waves in harbor
Wave diffraction into a bay

diffraction

diffraction is very important for radio communications !
diffraction is when waves bend around the corner of an obstacle .
diffraction wave behaviour

Medium gap : some diffraction, but mostly straight

Gap of wavelength size : most diffraction

The maximal effect is when the gap and wavelength are about the lapp size .
wave diffraction radio
Radio waves with wavelengths of kilometers diffract
over hills and through valleys so you can easily get reception .
wave diffraction microwave
But microwaves with wavelength of centimeters by and large go straight .
microwave dish tower

then radio waves are good at “ broad cast ” to many people, but microwaves are good at point-to-point communication .
And for microwaves the vector and receiver must be “ line of spy ” ( they can see each other ) .
A typical microwave antenna is a parabolic dish of about 0.3 m to 3 m in diameter, like on this construction :

 

Ionosphere

The ionosphere is an electrically charged layer of the amphetamine atmosphere that is between 75 and 1000 kilometer above the ground .
It is very authoritative for radio and microwave communication !
low to medium frequency radio waves get reflected off the ionosphere, so it is potential to receive radio signals from far away that have bounced their way to us .
radio microwaves earth
(Not to scale)
But microwaves can cut right through the ionosphere so they are full for communicating with satellites .

Signal and Noise

analog digital
information can be in analogue or digital shape .

Analog

data can be put onto a brandish by altering its acme or wavelength a little :
analog picture
A roll has a signal of this picture put into it .
As the wave travels it gets noise ( random changes ) added by early electrical activeness around it :
analog picture noise
When we try to recreate the visualize the result is not perfective !

Digital

But with digital we expect only certain values, such as 0s or 1s. so noise ( if not besides big ) can be overcome.

digital picture noise does not affect quality
even with randomness we still know every 0 and 1 and get a arrant double .

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