Ugh... You are so stupid...
This seems to be protocol for your robotic people. 
First of all, the speed of sound is clearly slower than the speed of light. Agreed?
The speed of sound doesn't have a set constant speed, it's just made out that way. There is no such thing as the speed of light. Light is merely a reflection of sound or a manifestation of vibration that makes sound that makes light be frequency change.
OK. Let's move on. As you may notice in a pond, no matter what the wavelength and the frequency of the ripples is, it doesn't change how fast they propagate, so how can light move that much faster than sound just because it has a different frequency?
You've seen a Newtons cradle, right?
You've seen one ball hit another and yet the end ball moves almost immediately, yet falls back and makes the first ball react almost immediately. Why?
Just like in a pond you can make waves react the same way if you have a barrier to your wave as you set it in motion. Now imagine someone tapping a stick into the pond, then again, quickly...and again and again, getting quicker and quicker.
Watch the ripples/waves.
As long as there is a constant wave pattern for that pressure there will be a constant end product from it.
To place it into a different context, it's like a radio or a phone or whatever you want to name.
If you wanted to build up a pressure in that stick before you unleash it onto the pond, you would get a snap crackle and pop. You get a rice krispy arc or to put it simpler, you get lightning that the person on the other side, sees and then hears what made it. Friction/vibration.
If light is purely a wave, how does it explain experiments like the 2 slit experiment?
What's tehre to explain. What's happening that makes what I'm saying, wrong?
What is your evidence about light being sound? Why would it be sound? Is there a reason?
The reason is simple. We exist because we are vibrations. That's it. No more thought needed.
It's like walking past a wall that shoots out a boxing glove punch which can vary in strength and pressure.
You can pretend that the boxing glove is something else if you want but it's going to dish out the same thing to you every day, except in variations that you can't rightly predict with any accuracy.
It's still basically a bat in the face with a boxing glove. The same as you will always vibrate even when you're a non thinking lifeless (to us) human shell. You'll stay vibrating until Earth stops vibrating, which will be never.
How can we have light in vacuum?
We can't and until people like you get a grip on what vacuum actually is, you'll spout nonsense.
Let me try carefully and quickly.
A vacuum is the ABSENCE of all matter. What does this mean?...it means that a vacuum basically does not exist. How can we visualise a vacuum that does not exist?
We can't. We just think we can because we are being duped by the science world to believe that space is as close to one as we can get, yet AS CLOSE is nothing as an explanation for a vacuum.
It's like you trying to hide behind a wall slowly and me shouting, " I can still see you but you're half disappeared. One more half and you will be gone. "
The truth is, you're not gone. You are still there. Now unless you literally disappear into the air, never to be seen or heard of again, you can be classed as disappeared in a sense but in actual fact, you are scattered and still exist as a scattering.
A vacuum is none of this. It's a nothing. It never existed except for a word.
You don't see it or feel it and you do not see anything in the sky that is it, as in what you see a space.
You see blackness. You see blackness because that's what you are told blackness is.....a vacuum of space or a near vacuum of space...or space with free moving particles...or space with EM radiation just travelling around it, etc.
You will not allow yourself to bother to open your own mind to see how silly it all is, because your trust in tefal heads is unconditional. They make you feel smart, because they are backed to the hilt as long as they follow protocol which includes feeding you what's put on their platter.
I see many people time and time and time again mention vacuum and SUCK. Vacuum do not suck because vacuums do not exist to us, except to misuse the word as badly as saying the big bang started from NOTHING.
As bad as believing you know what a black hole is. Or a wormhole in space. Or whatever else gets spewed out.
Get this into your head and make a point of keeping it there. You live under pressure. You live in a sea that you call atmosphere that is pushing you into the deck.
You are walking about and vibrating and creating waves as you do so, just like the bee that flies past your head that could be almost talking to you, if those vibrations from it's wings were fine tuned for your ears and understanding of your own vibrational alphabet or words from it.
You are merely a buzzing vibration to something else you live among that is not on your frequency.
You are a vibrational glow but you cannot see it, yet a bat can. You can see a firefly at night. What do you think it's doing? do you think it's poured petrol over itself and flying about screaming?
It's staying alive by vibration...by sound and frequency that's creating the light you see.
In your fictional vacuum, you cannot have any vibration at all. No waves. No friction. no life. Because the vacuum...the true vacuum that we can only think of, means the end of all vibration. Everything ceases to be anything, because all energy stops.
Where is the point where sound stops being sound and becomes light?
That depends on the pressures and waves and frequencies that create the vibrations that create the sound and light after effects that you see.
Imagine walking down an alley made of metal and you have a metal bar that you are scraping along it. If you walk along slowly whilst putting pressure on that wall, you hear a horrendous noise. Is it light?
Yes it is but not to you, because your ears pick it up and your body feels the vibrations, yet your sight is not geared to seeing a glow..but it's there. To find out, all you have to do is start running as fast as you can whilst dragging that metal bar and soon you'll hear the sound become less horrendous and the vibration will become less intense...but now you will see something that you couldn't. You see a glowing metal bar that will get brighter and brighter if you keep putting the energy in and increasing your acceleration, until it starts to melt.
You don't need to put yourself through this task. Just resonate a magnet and put some metal inside of the coil and it will glow without anything seemingly touching it...except atmosphere that is super vibrating at frequency and pressure is doing the very same thing to it as you were doing with your iron bar on the wall...except it appears different to your vision.
What are you even talking about?? Are you some sort of hipster who disagrees with mainstream science just because it is mainstream? What sense does all of that make? How can anything in your mind produce such a high frequency of sound that it creates light? It's ridiculous...
I don't like being filled with bullshit or potential bullshit, so I decide to work it out for myself. the only possible way to do that (considering our indoctrination has been severe) is to start from square one. Basically be reborn.
Start the Earth in motion and build it from there. Or I should say, try and figure out what The Earth would be doing and how it can manage to have such an abundance of life that just happens to be a circle of more or less, perfection, as in one mans waste is another creatures food and one man's death is another creatures life.
It's like we are all cigarettes that are glowing at the tip...all of different sizes and all of different packaging of tobacco in density. It's a case of who burns down quickest but also a case of each species asking for a light off the tip of another's lit cigarette end.
If you move fast your cigarette glows more and burns down faster. If you move slow, your cigarette burns down much less because the glow is not so intense.
Who wants to be a firefly and who wants to be a blue whale?
You do not understand science... A single WAVE can NOT propagate through a certain material faster if it has a different frequency. If you are tapping a stick in a pond, all you are doing is increasing the frequency of the ripples. You don't make them move faster. If the speed of sound in a certain material (say the atmosphere) is, say, 1000mph, then even if you increase the frequency, it won't move faster. It will just have a higher frequency. I think it's quite obvious that light is faster than sound. I have no idea what a Newton's cradle has anything to do with anything. Maybe you just thought it sounded cool.
If you are not familiar with the double slit experiment, this is what it says:
"In the basic version of this experiment, a coherent light source such as a laser beam illuminates a plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. The wave nature of light causes the light waves passing through the two slits to interfere, producing bright and dark bands on the screen—a result that would not be expected if light consisted of classical particles. However, the light is always found to be absorbed at the screen at discrete points, as individual particles (not waves), the interference pattern appearing via the varying density of these particle hits on the screen. Furthermore, versions of the experiment that include detectors at the slits find that each detected photon passes through one slit (as would a classical particle), and not through both slits (as would a wave). These results demonstrate the principle of wave–particle duality.""The reason is simple. We exist because we are vibrations. That's it. No more thought needed.
It's like walking past a wall that shoots out a boxing glove punch which can vary in strength and pressure.
You can pretend that the boxing glove is something else if you want but it's going to dish out the same thing to you every day, except in variations that you can't rightly predict with any accuracy."
What is your evidence about any of this? Is there a reason? Does it explain anything at all?
How can we have light in vacuum?
"We can't and until people like you get a grip on what vacuum actually is, you'll spout nonsense.
Let me try carefully and quickly.
A vacuum is the ABSENCE of all matter. What does this mean?...it means that a vacuum basically does not exist. How can we visualise a vacuum that does not exist?
We can't. We just think we can because we are being duped by the science world to believe that space is as close to one as we can get, yet AS CLOSE is nothing as an explanation for a vacuum."
I'm gonna explain to you something very very simple: how to create a near perfect vacuum and how to shine light through it. Take a glass box. Remove everything that is inside it. Then take a vacuum pump. Suck as much air out of it as you can. Take a laser or any other light source. Voila. Why do you have so much trouble comprehending that? By the way, there is vacuum everywhere. The space between atoms has no matter in it. That's a vacuum. I also don't know why you have such a hard time comprehending the darkness of space. Darkness is like vacuum. It doesn't really exist, it's just absence of light, just like vacuum is an absence of matter. If there is no matter to emit light, then you have darkness.
"Yes it is but not to you, because your ears pick it up and your body feels the vibrations, yet your sight is not geared to seeing a glow..but it's there. To find out, all you have to do is start running as fast as you can whilst dragging that metal bar and soon you'll hear the sound become less horrendous and the vibration will become less intense...but now you will see something that you couldn't. You see a glowing metal bar that will get brighter and brighter if you keep putting the energy in and increasing your acceleration, until it starts to melt."
That's not remotely what you say. You say that light is sound. What really happens is that you heat up the metal due to the friction. You also make sound. Everything that has a temperature above 0 Kelvin emits radiation, you just can't see it, because your eyes can't see it. The more you heat something up the more its light shifts to red, then white, then blue, etc. That's why it glows. Ok. Nice. You also produce sound because of the friction. So the sound is produced by vibrations due to the friction, and the light is produced by heat that is produced by the friction. Does this mean that light = sound? NO! It simply means that the source in this circumstance (the friction) is the same. It's like saying that if a cook makes a cake and then cooks a steak, the steak is the same thing as a cake.
"I don't like being filled with bullshit or potential bullshit, so I decide to work it out for myself. the only possible way to do that (considering our indoctrination has been severe) is to start from square one. Basically be reborn.
Start the Earth in motion and build it from there."
So you basically just decided to make your own version of reality. That's interesting, but if you still believe that it's actually reality, then you are delusional. It's an incoherent "reality" that explains nothing and makes no sense. If that is what you will, then fine. Just don't bother other people with it.
"If you move fast your cigarette glows more and burns down faster. If you move slow, your cigarette burns down much less because the glow is not so intense.
Who wants to be a firefly and who wants to be a blue whale?"
Are you high?