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
Unfortunately the real answer to your question is a bit long, because electromagnetic waves are different than any other kind of wave you are used to, in that there is no medium that the wave is traveling through, like water or air. They can even travel through empty space. But I will do my best.
Electricity and magnetism are related in an interesting way. If you run electric current through a wire near a compass, you’ll cause the compass to change direction. If you spin a magnet near a coiled wire, you will cause an electric current in the wire. They are related to each other, but in a strange, physically perpendicular way you’d never really guess on your own.
Hold your right hand out like you were making a finger gun. Pew pew. But now, also half-extend your middle finger to point to the left. Your thumb, index finger, and middle finger form a 3-way x/y/z axis. This is how electricity, magnetism, and physical force are related: a magnetic field in the direction of your index finger causes an electric charge in the direction of your middle finger, and both together cause a force in the direction of your thumb.
Now imagine you could sort of “grab” a little bit of empty space, and “pull” a bit of electric charge in one direction from nothing, with no physical object there. Almost like you were stretching a virtual rubber band. This would create a magnetic charge rubber band stretching the same amount, in a perpendicular direction. Now let go.
What’s interesting is that these two stretched rubbed bands kind of “tug” on each other, wanting to get back to neutral. So the perpendicular electric and magnetic forces pull each other back towards zero, but there’s nothing to stop them when they get there, so they keep going right past each other and end up stretching back out the same distance, but in the opposite direction, as from where they started.
Now they pull on each other again, back to zero, and again right past each other. Back and forth, back and forth. There is no “friction” to slow them down, so they are a permanently oscillating little bit of electricity and magnetism. How fast do they oscillate? Well, depends how far you stretched the little rubber bands to begin with. The more you stretched them, e.g. the more energy you put into creating your little packet to start with, the faster they snap back and forth.
But remember your little finger gun: the result of this oscillation between your index finger (magnetic) and ring finger (electric) directions results in a force in the direction of your thumb.
Meaning, your oscillating little “packet” of electric and magnetic rubber bands experiences a force, and it *moves.* How fast does it move? Well, it has no mass, remember. It has no inertia, ‘cuz it’s not made of “stuff.” So it moves as fast as anything in this universe can: the speed of light.
So it is a distinct little packet of energy that is moving through space like a bullet. But that packet is made up of oscillating electric and magnetic fields. The rate of the oscillation depends on how much energy created it to begin with. How much the rubber bands were stretched before you let go. But no matter how fast they oscillate, they still travel through space at the same speed of light. High energy packets will travel less distance before they return to their initial configuration. Lower will travel further. This is the “wavelength” that differentiates wifi, from visible light, from radio, or gamma rays.
[Here’s an attempt at showing this animated.](https://commons.wikimedia.org/wiki/File:EM-Wave.gif)
It’s very hard to actually draw this, as it’s a 3D thing with stuff wiggling along 2 axes while traveling in a third. So most depictions of electromagnetic waves simplify it significantly, as a static 2D squiggle on paper. And because the actual explanation is a whole lot longer and requires knowing about the relationship between electricity and magnetism (see length of above), most grade school science books just say “eh, close enough” and move on. Unfortunately, that simplification tends to cause the same confusion you have.
Unfortunately the real answer to your question is a bit long, because electromagnetic waves are different than any other kind of wave you are used to, in that there is no medium that the wave is traveling through, like water or air. They can even travel through empty space. But I will do my best.
Electricity and magnetism are related in an interesting way. If you run electric current through a wire near a compass, you’ll cause the compass to change direction. If you spin a magnet near a coiled wire, you will cause an electric current in the wire. They are related to each other, but in a strange, physically perpendicular way you’d never really guess on your own.
Hold your right hand out like you were making a finger gun. Pew pew. But now, also half-extend your middle finger to point to the left. Your thumb, index finger, and middle finger form a 3-way x/y/z axis. This is how electricity, magnetism, and physical force are related: a magnetic field in the direction of your index finger causes an electric charge in the direction of your middle finger, and both together cause a force in the direction of your thumb.
Now imagine you could sort of “grab” a little bit of empty space, and “pull” a bit of electric charge in one direction from nothing, with no physical object there. Almost like you were stretching a virtual rubber band. This would create a magnetic charge rubber band stretching the same amount, in a perpendicular direction. Now let go.
What’s interesting is that these two stretched rubbed bands kind of “tug” on each other, wanting to get back to neutral. So the perpendicular electric and magnetic forces pull each other back towards zero, but there’s nothing to stop them when they get there, so they keep going right past each other and end up stretching back out the same distance, but in the opposite direction, as from where they started.
Now they pull on each other again, back to zero, and again right past each other. Back and forth, back and forth. There is no “friction” to slow them down, so they are a permanently oscillating little bit of electricity and magnetism. How fast do they oscillate? Well, depends how far you stretched the little rubber bands to begin with. The more you stretched them, e.g. the more energy you put into creating your little packet to start with, the faster they snap back and forth.
But remember your little finger gun: the result of this oscillation between your index finger (magnetic) and ring finger (electric) directions results in a force in the direction of your thumb.
Meaning, your oscillating little “packet” of electric and magnetic rubber bands experiences a force, and it *moves.* How fast does it move? Well, it has no mass, remember. It has no inertia, ‘cuz it’s not made of “stuff.” So it moves as fast as anything in this universe can: the speed of light.
So it is a distinct little packet of energy that is moving through space like a bullet. But that packet is made up of oscillating electric and magnetic fields. The rate of the oscillation depends on how much energy created it to begin with. How much the rubber bands were stretched before you let go. But no matter how fast they oscillate, they still travel through space at the same speed of light. High energy packets will travel less distance before they return to their initial configuration. Lower will travel further. This is the “wavelength” that differentiates wifi, from visible light, from radio, or gamma rays.
[Here’s an attempt at showing this animated.](https://commons.wikimedia.org/wiki/File:EM-Wave.gif)
It’s very hard to actually draw this, as it’s a 3D thing with stuff wiggling along 2 axes while traveling in a third. So most depictions of electromagnetic waves simplify it significantly, as a static 2D squiggle on paper. And because the actual explanation is a whole lot longer and requires knowing about the relationship between electricity and magnetism (see length of above), most grade school science books just say “eh, close enough” and move on. Unfortunately, that simplification tends to cause the same confusion you have.
A wave is any thing that changes the average. Like the ocean is still until wind blows and it creates a wave, moving water up and down towards a direction. Light, radio, gamma, Wi-Fi, UV, Bluetooth etc. are all part of the electromagnetic spectrum. Which is, to simplify, a wave that has its own energy packets called photons. So depending on the frequency of the wave, they can either be massive, like radio waves, or small like gamma. Wi-fi, which is a microwave is in between. So when moving in the physical space, a larger wave would have more interference (like when you turn on a radio and you hear the fuzz or how old TVs had noise) but but since its a low frequency wave, it carries less energy. On the flip side, a higher frequency would carry more energy and information but for a shorter range before it becomes a longer wave then interference becomes are problem. (Interference can be anything…for radio it can be a mountain, particles in the wind, humidity etc. for microwaves it can be a thick wall, a person etc. also the waves are small so they can go in between atoms and their energy level is low enough that it doesn’t affect atomic structures.
Also the thing that travels is a photon when you look close, but its a wave when you zoom out. Wave-particle duality did a number to a lot of physicists. Also! It doesn’t need a medium. The wave moves faster in a vacuum.
(A photon is a massless particle that is a unit of energy. And it moves at the speed of light (which is also a photon).
A wave is any thing that changes the average. Like the ocean is still until wind blows and it creates a wave, moving water up and down towards a direction. Light, radio, gamma, Wi-Fi, UV, Bluetooth etc. are all part of the electromagnetic spectrum. Which is, to simplify, a wave that has its own energy packets called photons. So depending on the frequency of the wave, they can either be massive, like radio waves, or small like gamma. Wi-fi, which is a microwave is in between. So when moving in the physical space, a larger wave would have more interference (like when you turn on a radio and you hear the fuzz or how old TVs had noise) but but since its a low frequency wave, it carries less energy. On the flip side, a higher frequency would carry more energy and information but for a shorter range before it becomes a longer wave then interference becomes are problem. (Interference can be anything…for radio it can be a mountain, particles in the wind, humidity etc. for microwaves it can be a thick wall, a person etc. also the waves are small so they can go in between atoms and their energy level is low enough that it doesn’t affect atomic structures.
Also the thing that travels is a photon when you look close, but its a wave when you zoom out. Wave-particle duality did a number to a lot of physicists. Also! It doesn’t need a medium. The wave moves faster in a vacuum.
(A photon is a massless particle that is a unit of energy. And it moves at the speed of light (which is also a photon).
A wave is any thing that changes the average. Like the ocean is still until wind blows and it creates a wave, moving water up and down towards a direction. Light, radio, gamma, Wi-Fi, UV, Bluetooth etc. are all part of the electromagnetic spectrum. Which is, to simplify, a wave that has its own energy packets called photons. So depending on the frequency of the wave, they can either be massive, like radio waves, or small like gamma. Wi-fi, which is a microwave is in between. So when moving in the physical space, a larger wave would have more interference (like when you turn on a radio and you hear the fuzz or how old TVs had noise) but but since its a low frequency wave, it carries less energy. On the flip side, a higher frequency would carry more energy and information but for a shorter range before it becomes a longer wave then interference becomes are problem. (Interference can be anything…for radio it can be a mountain, particles in the wind, humidity etc. for microwaves it can be a thick wall, a person etc. also the waves are small so they can go in between atoms and their energy level is low enough that it doesn’t affect atomic structures.
Also the thing that travels is a photon when you look close, but its a wave when you zoom out. Wave-particle duality did a number to a lot of physicists. Also! It doesn’t need a medium. The wave moves faster in a vacuum.
(A photon is a massless particle that is a unit of energy. And it moves at the speed of light (which is also a photon).
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
A wave is a periodic disturbance in… something.
I’ll take three cases, getting less intuitive as we go.
In **water waves**, the disturbance (in… water) is at right-angles to the wave’s direction of travel.
In **sound waves**, the disturbance is a pressure wave – periodic compression in the packing of the constituent particles of some medium (air, water, solids) where the disturbance is in the same direction as the wave’s direction of travel. (The usual analogy is to a Slinky being pushed to get a compression in the coils travelling along the toy’s length.)
WiFi signals travel in radio waves. These are an example of **electromagnetic waves**. In these waves (which also include light, microwaves etc.) things get less intuitive, because we’re no longer talking about a disturbance in a physical medium; we’re now talking about a disturbance in paired electric and magnetic fields. These fields in a sense feed off each other and keep themselves going in a straight line; they don’t need any medium in which to travel.
A wave is a periodic disturbance in… something.
I’ll take three cases, getting less intuitive as we go.
In **water waves**, the disturbance (in… water) is at right-angles to the wave’s direction of travel.
In **sound waves**, the disturbance is a pressure wave – periodic compression in the packing of the constituent particles of some medium (air, water, solids) where the disturbance is in the same direction as the wave’s direction of travel. (The usual analogy is to a Slinky being pushed to get a compression in the coils travelling along the toy’s length.)
WiFi signals travel in radio waves. These are an example of **electromagnetic waves**. In these waves (which also include light, microwaves etc.) things get less intuitive, because we’re no longer talking about a disturbance in a physical medium; we’re now talking about a disturbance in paired electric and magnetic fields. These fields in a sense feed off each other and keep themselves going in a straight line; they don’t need any medium in which to travel.
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