Define the Characteristics of Radio Frequency (RF)

0:05Well, as it turns out, our light waves can behave at pretty much any frequency. We're talking about really, really low frequencies like my 3 hertz example to really, really high frequencies. But we're not just talking about gigahertz and terahertz. We're talking about much, much greater frequencies. So when look at small frequencies to very large frequencies, this forms what we call the electromagnetic spectrum. In this video, we want to take a look and see what exactly the spectrum is, where on the spectrum our Wi-Fi falls, and then start to understand how it all ties together. Let's take a look. As humans, we are actually able to tell what frequency light is behaving at because different frequencies of light turn into different colors for us, and so even the yellow of my pen that I'm using right now is a different frequency than, let's say, the blue of this text up here, and our eyes are able to distinguish that so long as our eyes are working like they're supposed to.

0:54And so oftentimes what we can compare this to specifically is the rainbow, and I already mentioned the colors of the rainbow before. We had red, orange, yellow, green, blue-- sometimes we throw indigo in there-- and then violet. And we see this specific range of colors, especially when we look at, for example, a rainbow in the sky and we see all of these different colors lined up with one another. Well, that's because of the frequency of light. And so what we're really saying is that red is the lowest frequency of light and violet is the highest frequency of light, where orange lies somewhere in the middle.

1:30But orange is less than yellow, and yellow is less than green and so on and so forth. And so it's pretty fascinating how we can interpret different frequencies as different colors. But even more fascinating is the fact that there are just a ton of frequencies that we cannot see, and those would be frequencies that are lower than red and frequencies that are higher than red. And so we have to be really cognizant, I suppose, of the fact that the electromagnetic spectrum is so much bigger than we can perceive with our human eye.

2:02And so it's lovely to look up into the sky and see these beautiful rainbows, but there's a whole lot of other colors that we just can't see. And so when we talk about these colors-- or maybe I should call them frequencies-- what we find is that we can go as very, very low as we want down to, again, a single hertz, 1 hertz, 2 hertz, 3 hertz. And then we can go higher than what we can see, so even starting with terahertz and going to petahertz, for example, and exahertz. And we can go all the way up to, let's say, something times 10 to the 18th or times 10 to the 20th hertz, and we're talking about an enormous number of cycles per second.

2:39And because this is a spectrum, we tend to break this down into what we call regions, and so I'm just going to throw some barriers up here and understand that when we're talking about a particular region we're talking about a range of frequencies that our signals would be classified as. And so we can start right away by talking about the regions directly outside of red and violet. And we have special names for those, and you've probably heard of them. We have the infrared region, and we have the ultraviolet region. Now, infra, if we look at the English word there, what exactly is that saying?

3:12Infra means below, and so infrared has always been talking about the fact that it is the frequency region below red light. Likewise, ultra-- we talk about ultra. Some superheroes seem like they have ultra in their name. It means above. It means high. It means-- maybe we like to think of it as powerful, but ultimately it's the opposite of infra. Infra means below. Ultra means above. And so we're talking about ultraviolet. This ultraviolet region means that it has a higher frequency than violet.

3:45And so these are the first two regions that we tend to talk about a little bit because we're concerned about UV rays. We need to be careful with that because they can give us sunburn and some even worse health effects as a result of being exposed to high levels of frequency, these radiation types. And so as we look higher than ultraviolet, we get into the X-ray domain, and X-rays-- a lot of us are probably familiar with those just from the medical world perspective.

4:15I know I can go into the hospital. I can get an X-ray of my broken hand. It'll show me all of my bones. But really what they're doing is they're shining X-rays through my hand against a photoelectric plate that's essentially going to capture an image of what's happening inside of my hand. And so that's why we have to use X-rays for that. But again, this is like UV. It's very, very high frequency, and so we've got to be careful with this. It has very negative health effects, which is why hospitals are tracking how many X-rays we have.

4:45And the attendant who manages the X-ray-- they have to run behind a shield because if they're exposed to X-rays constantly that would be very dangerous. And then we have gamma rays up here. Yes, if you follow comic books you probably have heard of gamma rays, but that's the comic book version of it. There are real-life gamma rays. We don't have any practical uses for it that I'm aware of. I'm sure there's something out there for these, but ultimately, gamma rays are just anything above X-rays. So it just kind of keeps going and going.

5:15And so now we look at something-- at the frequencies lower than infrared, and the biggest one is right-- whoops, I started spelling the wrong one. The biggest one is the microwave region, and so, yes, this is where our microwaves that we use in our kitchens operate. And that's one good. Other than-- we can possibly think of something more applicable to the course, which is Wi-Fi. This is where we fly lives. It lives at a much lower frequency even than infrared, let alone visible light. And so when we talk about the health implications of Wi-Fi, the reason why science says that Wi-Fi radiation is safe is because not only is it below the frequency of some of these dangerous rays like ultraviolet and X-rays, it's actually lower than the frequencies of visible light.

6:02And so we're not just talking light from the sun because that has ultraviolet light in it, but we're talking about just the colors that are reflecting off of my walls having much, much higher frequency, we just said, 400,000 hertz or 400,000 gigahertz, rather, versus the 5 gigahertz that my Wi-Fi is operating at. And so when we talk about the wavelengths-- the wavelength is like 6 centimeters. That's a pretty large wavelength. And so we're not as concerned about Wi-Fi signal causing damage in the same way that UV and X-rays-- they can actually jump into our cells and destroy parts of our cells.

6:43So from a health perspective, that's why we say it's safe. It's the same reason why we say using microwaves in our kitchen-- that it's safe for using on food because all it's doing is heating up the water. It's not actually injecting radiation into our food. It's in the same way that shining a flashlight on our food wouldn't actually cause our food to have problems. And so the last region down here-- this is what we call radio waves. The reason why it's called radio waves is because we use these for broadcasting radio and TV.

7:16And so especially back before streaming services and when we have an antenna outside of our house and we're receiving signals for our radio-- in fact, we still use this in our cars extensively when we're tuning into the radio, et cetera. That's where we're getting our signals from. And so they operate in the radio space. But again, as I mentioned earlier, I think some people hear radio waves and assume this has to do with audio. It has nothing to do with audio. It can convert into a data, and so that data can be a picture like on our TV.

7:49It can be audio like the TV audio. It can be audio like our radios. But ultimately, it's doing exactly what Wi-Fi does, which is encoding information into these different waveforms. And it's operating at such a low frequency that, number one, it's very, very safe, but also, number two, it can go really, really far much, much further than any of the waveforms that are in a higher part of the spectrum. And so that's the other part we want to talk about here is how frequency relates to our distance because as we might imagine, it doesn't do me much good if my house where I've got my TV antenna up here, let's say-- so I'm not sure how to draw this TV antenna.

8:32There we go, some kind of Yagi antenna. And I need to be as close to the TV station with a big antenna on it or what have you. I need to be this close to the TV station just to get that signal in the same way that need to be right next to an access point to get Wi-Fi signal. Now, instead, we want this to be miles or many, many kilometers away. In fact, we need this to be sometimes in adjacent cities, and so this is why the lower frequency is used, because the lower the frequency, the greater the distance that signal can propagate using the same energy levels.

9:07And so this is why, if I step out of my house and I just take a few steps away sometimes, my Wi-Fi doesn't quite make it out of my house to my outdoor area. Now, I might see my neighbors' Wi-Fi or something along those lines, but oftentimes the quality is very, very low. And certainly I'm not going to be able to get it miles away from my house, and so that's because we're using a much higher frequency. We're using that 2.4-gigahertz frequency or the 5 gigahertz or now the 6-gigahertz spectrum, and so these are much higher frequencies than my radio and TV waves are using.

9:41Now, this doesn't just affect our distance. It's also going to affect our propagation. When I say propagation, really I'm talking about through things. So we're talking about walls. We're talking about buildings, whatever it is that's impeding our path. And so once again, I might have a bunch of houses, or I might have a building here between the TV station and my house, and this signal is going to pass through just fine because of the lower frequency. And the same way that my Wi-Fi-- I might have my floor plan look something like this, where I've got a hallway here.

10:14And I've got the access point in the hallway, and I've got two rooms right next to this access point. Well, I'd expect that the access point is going to be able to communicate into these rooms. It can communicate through walls because it's a much lower frequency than all of these frequencies up here, even visible light. So this is one reason why visible light can't go through walls. However, visible light, we understand, can go through things that we might call translucent. Translucent means that I can get partial amounts of light through something. So maybe I think about a candle.

10:46If I shine a flashlight against a candle, I can see that light go through the candle. I can even see the flashlight go through my hand to some extent. Visible light is able to go through some materials. But certainly, as we get into UV and especially X-rays and gamma rays, it's much harder for those types of radiations to penetrate things. That's why we use lead vests when we're taking X-rays because it blocks those X-rays solid. It makes it so that they can't get through, whereas certainly a radio wave is going to be able to go through that same type of shield. So understanding that the higher the frequency we get the lower the distance that our propagation is going to go and the more that walls, and buildings, and obstacles are going to impede our communications.

11:28So when it comes to our key takeaways, one of them is simply going to be that it's really cool how our eyes can detect different frequencies of light by representing them to us as different colors. So when we're seeing blue versus red, we're truly seeing completely different frequencies. Red is as low of a frequency as we can see, and blue, especially violet, is as high of a frequency as we can see. So next, the electromagnetic spectrum we see is-- yeah, it's got the visible light right there in the middle, but it really goes very, very far, way higher and way lower on the spectrum.

12:00And so it's important that we can identify the different regions and especially understand that Wi-Fi communications, and cellular, mobile data, those kinds of things-- they all operate within the microwave part of that spectrum. Now, lastly, as we talked about, the higher the frequency goes, the less far that those waveforms are going to be able to propagate. So it's going to have more problems with obstacles. It's going to have problems even just in free space, just trying to get across things. But ultimately, this is why we use the lower frequencies for our communications, because we want our communications to be able to go certain distances.

12:37And so when we look at the applications, sure, TV and radio-- that might be coming from the next city over. It needs to be a very low frequency so that those waveforms-- remember how long those waveforms can get at the lower frequencies. They are going to have an easier time passing through obstacles, whereas then as we get into higher levels of radiation or higher levels of frequency, that's going to be harder and harder to do. I hope this has been informative for you, and I'd like to thank you for viewing.