Hi all: Why is it that we have a dozen or so different electromagnetic wave types and yet every one of them can be used for analog and digital communication?
Thanks!
In: Physics
The electromagnetic spectrum, going from longest wave-length to shortest, is radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, then gamma waves. Radio waves, obviously, are used for communication, and of course visible light. Can any of the others feasibly be used for long distance communication too? I don’t know…
There really aren’t different type of electromagnetic waves. They are all the same and vary by frequency and amplitude. You see colors, those are electromagnetic waves of different frequencies. Amplitude would be the brightness of the light. Most frequencies of the EM spectrum you just can’t see because our eyes only detect a really narrow range of frequency.
Using visible light as an example: for analog you could vary the brightness of light (amplitude modulation; do it with radio waves and you might call it AM for short), or you could keep the brightness constant and change the color (frequency modulation; do that with radio and you might call that FM).
Digital signals are just when you use an analog signal to represent “1” or “0”. You can do that with amplitude (when the light is off or below a certain brightness it may be 0, and above a certain brightness, a 1). Likewise you could use frequency to encode the 1’s and 0’s, perhaps closer to red is a 0 and closer to blue is a 1.
The advantage of digital is that you can chose ranges of amplitude or frequency (usually frequency), that make it really clear when something’s a 1 or 0 AND there are tricks when sending digital information where you can detect and fix errors in communication, so the receiver has a very good chance of getting a perfect copy of the message sent, even if there’s stuff affecting the signal.
Non-electromagnetic waves can also be used for communication in pretty much the same way. You can throw rocks in a calm pond and treat the waves in water as a form of communication. The frequency and bandwidth is just slow because it’s easier to throw photons than rocks.
A couple things:
They are all just different frequencies of the same phenomena. The different frequencies have different properties, but if you can build a detector for them, technically they are all usable for communication. Of course, there are obvious downsides to communicating via, say, gamma rays.
As far as digital vs analog? All digital signals originate as analog ones. (All signals are a sum of sine waves of varying frequency, amplitude, and phase.) If you take a “square wave” and zoom in on an oscilloscope, you can see just how analog it is.
There’s one type of electromagnetic wave. It’s frequency affects what you’re referring to as “type”. (It also affect how it propagates through matter like air as well as how directional it is.)
Essentially, the different types of electromagnetic waves vary in frequency and wavelength which allows for different applications and efficiencies in communication. However, the fundamental principles of encoding and decoding information can be applied to any type of wave, whether analog or digital.
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