I really can’t grasp the concept of waves. I can imagine it a bit for sound waves: a speaker has a surface that pushes air, and the moving air eventually pushes the membrane in our ears.
But I’m confused about wifi etc. What exactly is the thing that physically travels? Is it air or something else? Does it physically move in a wavy pattern?
Edit: thanks for all the answers! But damn I’m overwhelmed. It’s gonna take me days to read and fully understand the answers. But thanks!
In: 87
Good question, and it IS really confusing. Starting with the sound waves you understand, these are pretty simple, they are known as mechanical waves. Exactly like the waves on the top of water, these are caused by the movement of particles causing the particles next to it to move. Without these separate particles to move, the wave cannot continue, which is why, for example, sound does not travel in space.
For WiFi, radio, etc., these are known as [electromagnetic waves](https://science.nasa.gov/ems/02_anatomy). These are actually the same thing as light, radiation, microwaves, etc. They are all caused by electromagnetic energy. This is actually the movement of photons, which are particles that have energy and momentum, but no mass (in the normal sense of mass, we’ll skip details about that since this is ELI5). And, yes, they move in waves – they act like both particles and waves. This is how polarized sunglasses work – because light is traveling in waves, there are a lot of tiny lines on the lenses, so the waves have to be moving the right way to travel between the lines. Think of throwing a frisbee at a picket fence – the frisbee has to be oriented just right to pass through the fence slats.
Photons always travel at the speed of light, so we use that to measure/classify the [different types of energy](https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html). The distance between the crests of the waves is known as the wavelength, which is one way to measure. Another is how many waves happen per second, which is known as frequency, and it is measured by “hertz”, with 1 hertz being a wave with 1 crest as it travels 1 second, 2 hertz being a wave with 2 crests as it travels 1 second, etc. We can also measure these in terms of how much energy they have, which we measure in electron volts. because of the speed of light constant, all of these are related to each other, so if you know one, you know them all. Radio waves, microwaves, infrared/UV/visible light, x-rays, gamma rays, etc., are all the exact same thing – photons moving in waves, but at different wavelengths.
It propagate thru Space itself. Space is not empty place, it have Its own energy level And it never goes to absolute zero temperature And stays on ~2°K, it very much looks like sound wave, but you should know the molecules of air dont travel with the sound wave. Take long straight rope And Swish with one end, the rope Will form wave which travel on the rope, rope in this case can be air for sound Waves And/or Space for energy Waves. Also every energy Wave Is same as visible light, you just can’t see it. From physics perspective visible light, UV, radio, WiFi, microwave, etc. Is the same thing with different frequency.
A simplified experiment to get an initial idea about waves.
Have someone hold one end of a rope and you hold the other and stretch it taut between you both. Get the other person to move their end of the rope up and down fairly quickly (like a “wave”). Done properly, you should feel your end of the rope trying to move up and down as well. If the rope is long enough you might even see a “wave” moving from one end to the other as a disturbance.
Essentially what is travelling is that wave as the rope just stays between the both of you. This is how radio waves work but the rope is replaced by an electromagnetic field and the disturbance will be seen as changes in that field. That disturbance is caused by changing currents/voltages in an antenna which propagates the disturbance to the field.
If you go deeper into physics, it gets a bit more complicated but for the purposes of things like radio, wi-fi etc, this model is generally what is used to describe and design things to work.
Good question, and it IS really confusing. Starting with the sound waves you understand, these are pretty simple, they are known as mechanical waves. Exactly like the waves on the top of water, these are caused by the movement of particles causing the particles next to it to move. Without these separate particles to move, the wave cannot continue, which is why, for example, sound does not travel in space.
For WiFi, radio, etc., these are known as [electromagnetic waves](https://science.nasa.gov/ems/02_anatomy). These are actually the same thing as light, radiation, microwaves, etc. They are all caused by electromagnetic energy. This is actually the movement of photons, which are particles that have energy and momentum, but no mass (in the normal sense of mass, we’ll skip details about that since this is ELI5). And, yes, they move in waves – they act like both particles and waves. This is how polarized sunglasses work – because light is traveling in waves, there are a lot of tiny lines on the lenses, so the waves have to be moving the right way to travel between the lines. Think of throwing a frisbee at a picket fence – the frisbee has to be oriented just right to pass through the fence slats.
Photons always travel at the speed of light, so we use that to measure/classify the [different types of energy](https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html). The distance between the crests of the waves is known as the wavelength, which is one way to measure. Another is how many waves happen per second, which is known as frequency, and it is measured by “hertz”, with 1 hertz being a wave with 1 crest as it travels 1 second, 2 hertz being a wave with 2 crests as it travels 1 second, etc. We can also measure these in terms of how much energy they have, which we measure in electron volts. because of the speed of light constant, all of these are related to each other, so if you know one, you know them all. Radio waves, microwaves, infrared/UV/visible light, x-rays, gamma rays, etc., are all the exact same thing – photons moving in waves, but at different wavelengths.
A simplified experiment to get an initial idea about waves.
Have someone hold one end of a rope and you hold the other and stretch it taut between you both. Get the other person to move their end of the rope up and down fairly quickly (like a “wave”). Done properly, you should feel your end of the rope trying to move up and down as well. If the rope is long enough you might even see a “wave” moving from one end to the other as a disturbance.
Essentially what is travelling is that wave as the rope just stays between the both of you. This is how radio waves work but the rope is replaced by an electromagnetic field and the disturbance will be seen as changes in that field. That disturbance is caused by changing currents/voltages in an antenna which propagates the disturbance to the field.
If you go deeper into physics, it gets a bit more complicated but for the purposes of things like radio, wi-fi etc, this model is generally what is used to describe and design things to work.
To break this down as ELI5 as I can:
Radio only consists as a wave in the sense that something about is cyclical, meaning it repeats itself. In this case, it’s the voltage that makes it a wave, because the voltage changes back and forth. It needs to do that in order to generate the “wave” in the first place.
Think of it like this. You have a bowl of water, and you stick your finger in the water, but otherwise don’t move it. What happends? The water level raises up a bit, but is otherwise unchanged. Now wiggle your finger back and forth. Doing this creates waves in the water, and the faster you wiggle your finger the faster the waves seem to get.
Radio works much the same way. Stick up an antenna and put a current at a constant voltage through it, and all you’ll do is contribute to the overall ambient electromagnetic energy in the area (we call this “raising the noise floor.”) To actually get a signal through, you have to “wiggle” the voltage back and forth to “create the waves.” The rate at which you “wiggle” the voltage is the frequency of the signal. Your local radio FM station on 101.5? It’s “wiggling” the voltage 101,500,000 times per second. And when you draw that voltage change on a graph, it looks like a wave (it’s mathematically represented as a sine wave).
Hope this makes sense.
To break this down as ELI5 as I can:
Radio only consists as a wave in the sense that something about is cyclical, meaning it repeats itself. In this case, it’s the voltage that makes it a wave, because the voltage changes back and forth. It needs to do that in order to generate the “wave” in the first place.
Think of it like this. You have a bowl of water, and you stick your finger in the water, but otherwise don’t move it. What happends? The water level raises up a bit, but is otherwise unchanged. Now wiggle your finger back and forth. Doing this creates waves in the water, and the faster you wiggle your finger the faster the waves seem to get.
Radio works much the same way. Stick up an antenna and put a current at a constant voltage through it, and all you’ll do is contribute to the overall ambient electromagnetic energy in the area (we call this “raising the noise floor.”) To actually get a signal through, you have to “wiggle” the voltage back and forth to “create the waves.” The rate at which you “wiggle” the voltage is the frequency of the signal. Your local radio FM station on 101.5? It’s “wiggling” the voltage 101,500,000 times per second. And when you draw that voltage change on a graph, it looks like a wave (it’s mathematically represented as a sine wave).
Hope this makes sense.
To break this down as ELI5 as I can:
Radio only consists as a wave in the sense that something about is cyclical, meaning it repeats itself. In this case, it’s the voltage that makes it a wave, because the voltage changes back and forth. It needs to do that in order to generate the “wave” in the first place.
Think of it like this. You have a bowl of water, and you stick your finger in the water, but otherwise don’t move it. What happends? The water level raises up a bit, but is otherwise unchanged. Now wiggle your finger back and forth. Doing this creates waves in the water, and the faster you wiggle your finger the faster the waves seem to get.
Radio works much the same way. Stick up an antenna and put a current at a constant voltage through it, and all you’ll do is contribute to the overall ambient electromagnetic energy in the area (we call this “raising the noise floor.”) To actually get a signal through, you have to “wiggle” the voltage back and forth to “create the waves.” The rate at which you “wiggle” the voltage is the frequency of the signal. Your local radio FM station on 101.5? It’s “wiggling” the voltage 101,500,000 times per second. And when you draw that voltage change on a graph, it looks like a wave (it’s mathematically represented as a sine wave).
Hope this makes sense.
I don’t have an answer and have the same question as OP. I feel like the answers (so far) aren’t answering the question or not explaining why there may not be an answer.
Everyone is explaining what photons are and their properties but not “where” and/or how they propagate, or if there is any medium in which photons travel. I think that is what OP is asking (and so am I)
My understanding is that there is the electromagnetic field, which is all around, everywhere. Photons are little pulses through this field, that’s the particle part, and the frequency of the pulses is the wave part.
No idea if this makes sense.
ELI5: When people say photons or electrons are wavelike they literally mean “like a wave”. Notice the language, no one says it IS a wave, but it’s LIKE a wave. Ultimately you can only observe the end result of the photons, and the way we explain that end result is to say “wow, if this was a wave, it would make a lot of sense”. You can even treat it as if it were a wave, and a lot of really interesting math *works*. So your next question, if it looks like a wave and it talks like a wave, then it’s a wave? Not quite, because there is also results from observation where it looks like a particle. So you have the situation where something acts these certain ways, but we are unable to firmly put it into one category or the other. Don’t try to find an analogy or something that explains how a photon works compared to waves in a pond, because it doesn’t exist. It’s an entirely separate thing. The only way you can describe the behavior of a photon is to say it behaves like a photon!
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