Hello, are you okay? Yeah, good. Okay. So obviously we had a trial lesson last week and we were looking at reflection, refraction, etcec what have you been doing in class this week in science? Inside for physics? We did the thing that we did last lesson. Oh, you so you did went through refraction in detail. Yeah and we like used like a glass block and then put on the paper and draw the line. Yeah, okay, perfect for biology. Gone. We had a test and be like, it takes long. Oh, interesting. So you're doing breathing probably at the moment I say we're doing like human bodies. Yeah like bones and like Yeah, okay, no problem. So what we're going to do today is we're going to continue with the waves topic. There's not much left to it. So once we've done this, this will be the end of the waves topic. So you'll kind of be ahead in that for class and then we can move on to a different science when we have an next item. So we're gonna to talk today about waves and waves properties. Now up until this point, we've obviously looked at reflection, refraction. We've kind of talked about how light behaves primarily and how waves behave. But we haven't really talked about other types of waves because light isn't the only type of wave that exists. Light is only one of seven different types of electromagnetic radiation, which we will talk about today. So we're going to talk about waves and wave properties, two different types of waves, and the way to calculate things like the amplitude, the frequency, etc. So first of all, I'm going to start with a little definition about waves. A wave is a vibration that travels, that transports energy. So a wave is a vibration that transfers energy, and from one place to another, transfers energy from one place to another without transferring any matter. Okay. So from your studies so far, what would you say the term energy means and what types of energy can we have? Maybe electricity Yeah okay. Electrical energy, Yeah any others maybe like what's cool? The solar energy ity, like solar panels? Yeah that would cost probably as light energy. Things as well, like a chemical energy, kinetic energy. You were aware of that one. Have you studied that one in science this year? Kinetic energy. Okay. Okay. They're just different types of energy. But generally energy, like light energy and heat energy, they are transferred in what we call waves. Now the term matter as well. I'm saying that no matter is transferred, what about that word? Are you familiar with that one? Okay, matter is anything with a MaaS. So anything with MaaS and that takes up space. So anything with MaaS that takes up space. So for example, we are made of matter, okay, because we have a MaaS and we take up space. Your laptop is made of matter because it has MaaS and it takes up space. But the the less obvious types of matter are maybe things like air. So a lot of the time students think that air isn't matter because we can't hold it. But matter isn't necessarily something that you can hold. It just means that it's made up of particles, of atoms, of elements. So if something is made of atoms 's elements, it has MaaS, right? Even if it's a very, very, very, very, very small MaaS like air, the MaaS of air is very small, but it still exists. It's still there. Just because we can't see it doesn't mean it's not there. So anything with MaaS that takes up space, and I'm just gon na add here, matter is made up of atoms. That's the smallest particle of the matter. So whether it's an element, whether it's a compound, whether it's a mixture, all of those things are classed as matter. So actually, what we're looking at today is the opposite of matter. It's not matter at all. It's something that doesn't have atoms or elements or anything like that. So when we talk about energy or light, for example, we often find it difficult to describe what those things are because they're not made of the standard materials that we are quite familiar with. So for example, light, if ever you're talking about light in a formula, so for example, photosynthesis, you talked about photosynthesis in biology this year yet or ever. I feel we're talking about that, but at this point, I remember what it means. Okay, that's fine. So photosennthesis is the process by which plants, they absorb light and they produce sugar as a result. Now, when we write the formula out, we can write carbon dioxide, we can write glucose, we can write water, we can write oxygen. But what do we write for light? So like oxygen is O2, carbon dioxide is co two, water is H2O, right? They're all the molecular formulas of those substances. But what is it for light? There isn't a molecular substance. There isn't a molecular formula because it is not made of atoms. And this is where waves come in. So waves, remember, they are vibrations that transfer energy without transferring any matter. So nothing actually moves. Well, no specific pieces of matter, no atoms or elements move. It's more of vibrations. Okay, go on. And so I think we learn about there's light waves and ones are called sound waves. I think one of them is longitudinal waves and the others is transverse waves. Yeah, fantastic. Yeah well done. So great work. I love that point. This is what we're gonna to do today. We're gonna to talk about the properties of transverse waves and longitudinal waves. Okay, we're gonna start with transverse waves actually. So I'm gonna to draw a transverse waves. So tell me whilst I'm just writing this word out, what do you remember about transverse weights? What did you learn that you think you can PaaS on the transverse wave is like. It's like the sea wave. It's like Yeah going up and down. So these are waves that have oscillations, we call them, which are the up and down a bit. That's an oscillation. So the bits that go up and down. That are a 90 degree angle. To the direction of travel. Okay, so if this is my wave diagram, Yeah, here is my wave. So we usually put them on a little bit of a graph like this. So the wave looks like this up, then down, then up, and then down again. So this wave would be traveling in this direction. It's transferring energy from left to right. Bye. So that's the direction of travel, but the oscillations are going up and down, right? So there's the oscillation. So see how that's like a 90 degree angle to the direction that the wave is traveling. So if we were to watch this wave moving, it would be moving forward from left to right in my diagram. But the oscillations are going up and down, up and down. So this is a transverse if all waves except for sound waves are transverse, okay, so all waves that we're gonna to talk about except for sound waves are transverse sed. So I copy the Yeah cool just one sei'm just going to write this so always waves except for sound wave Yeah as soon as I've just written this and then I'll put the screen back up our transverse okay, Yeah can you see everything you want to copy there? Yeah Yeah it's fun, okay. So a couple of examples would be light waves. Water X -ray waves, you'll know that on too. So they're just a few examples of the types of waves, okay? Okay, right. So what we're going to learn about is a few of the wave properties. Okay, we're going to start with amplitude. So wave properties help us to determine certain features of the waves and give us an idea when it comes to sound waves. These can help us to predict what the sound actually sounds like. I think a lower amplitude is I'm like, isn't like how do I come right here? No, no, you can't because I've got the screen sharing. But just tell me, what do you what do you think? So I think it's the. You know the diagram you did like above, I think it's the 90 degree angle stuff. It's the 90 degree angle like and the line from the middle to the top, Yeah, it is the middle to the bottom, it is well done. So the amplitude is the maximum height of a wave from the center point. So this line that I've drawn in the middle, it's a bit like the line of normal. Well, we do also call it the line of normal that we drew last week when we were talking about reflection and refraction. So the amplitude of a transverse wave is the maximum height of the wave. Okay? So the amplitude now, if a wave sequence is like of a certain light or of a certain sound, all of the waves will have the same height. So the amplitude will be the same all the way along. So the amplitude of a transverse wave. The amplitude of a transverse wave is the. Maximum height of the wave from the central line. Okay, so from the central line. Now the amplitude can tell us a few things about the properties of the type of energy it is itself. So for example, in light waves, so a taller amplitude or a larger amplitude, so a larger amplitude. For light waves, if we were measuring light. Means a brighter light. Sorry, just 1s. There's just someone at my. About that, right? So a larger amplitude for light waves means a brighter light with sound waves. Did you talk about this in class? Bways? We talked about it. We just know that it's like like lines like. Yeah, so with amplitude Yeah, with amplitude and sound, if you have a large amplitude, so the wave is taller, it means the sound is louder, so it means a louder sound. Okay, so the larger amplitude for sound, so a larger sound. And then finally for water, this just means physically a big wave. Okay? So a larger amplitude for water means a taller wave. Now water is different to the others that we're talking about because sound, well, actually sound and water are different. Light and water, let's compare those two. So light, as I said, it isn't made of atoms and elements. We can't actually see light being transferred. Yes, we can see the outcome of that light being transferred. We can see images, we can see colors, but we actually can't see the waves of light passing around us. Whereas with water, we can. So you know if you watch water waves, you can see up and down. Yeah, exactly. So you can see that because with water, it is matter. Matter is water is matter. It's made of atoms and elements. Same with sound, okay? Because do you know when you were talking about sound in class, if we make a noise, how does it get from one end of the room to the other? How does sound travel? So the sound waves pushes each other and like bounce to the particles and the light makes sense. Particles of what? What is it that the particles of air, liquids or solid? Exactly. Well done. So because sound is the transfer of energy via air or liquids, or it can also go through liquids and solids. Of course, it's actually quicker in there, but yes, absolutely. So the molecules of air are what helps the sound to transfer. So actually sound does use matter, whereas light doesn't. So let me ask you another question. Why couldn't light sorry, why couldn't sound PaaS through a vacuum? So for example, there's no sound in space. Why is that? Because there's no particles in space. So the sounds can't get pushed by the other the particles. Yes. So there's no particles in space. So there's nothing to transfer it. There's nothing to Carry it. Okay. So this is the amplitude that we've talked about there, and that can mean something different depending on the type of wave that you are looking at. So with a sound wave, it means a larger sound, a louder sound. With a light wave it means a brighter light. And with a water wave, it just quite literally means a taller wave, a bigger wave. Okay. What about the term frequency then? Did you learn about that? And can you tell me what frequency is. Frequency, it's like. How fast? Like for example, in sound waves, is that the wavelength? Isn't it? It's related to the wavelength for sure. Yeah, Yeah. So the frequency in the wavelength are negatively correlated, which means that as one goes up, the other goes down. So let's do a low frequency wave first of all. So I'm just gonna to do a low frequency like this. And then a much higher frequency wave like this. Okay? So the frequency is a measurement of how many waves waves cycles there are per second. So if I said that in my diagram, this whole timeline was equal to 1s. So there's zero and there's one. Okay? And again, here's zero and here's one. So the number of complete wave cycles that I can see in my first diagram is one. There isn't another one after that because I can't see the other pep, so this is one full wave cycle. So my frequency would be one. Did you learn? What do we measure frequency in? A T yes. So hurt is the measurement of one wave per second. So hertz is another is like a simple way of saying waves per second. So this one down here, let's start with the peak. So wehave, one, two, three, four, five, six, seven, eight, nine, ten. So one, two, three, four, five, six, seven, eight, nine, ten. So in the same time period we have ten times as many waves. So the frequency of the wave below would be 10 hz, which is just equal to saying ten waves per second. Now, what do you think the frequency tells us about sound, for example? Oh, I know. It's how the picture of the sound because yes, because our teacher did like this was it called this wave generator stuff and then she used on the like iPad and did like this frequency test to see how high how how many hertz and we can can't hear it. I think my hires just like to know like 19000 something hurts. Okay, also you did an individual text. No, we did like this like Oh, this class test. If you can't hear me, just put your hands down. Oh interesting. So yours was 19000. You said that was the highest you could hear. And what about the lowest? So the highest I think human can hear say 20000 not Yeah 20000. Usually we say it ranges from 20 to 20 thousand. Yeah, okay, 20. I Yeah I think the lowest I can hear is like 50 or something. Oh, interesting. I've never done that task before. It would be interesting to see actually, was there many people in your class that could hear right up to the top and right down to the bottom? Yes, Yeah, quite a few. So Yeah, that's a that's a really interesting thing that you've done in class. Actually a low frequency wave would be a low pitch sound. Humans can generally hear a minimum of 20 hz. So humans can hear here minimum, usually because we say it's 20 to 20. So 20 hz to 20 khz, which is equal to 20000 hz. And then a high frequency wave is equal to a high pitched sound, which we can hear a maximum of about 20000. It would be a high pitched sound. With a maximum of about 20000 hz. Okay? So that would be kind of the range of humans. So humans can hear 20 to 20 thousand. So human range equals 20 to 20000 hz, or 20 khz, which is generally the highest frequency that we can hear. Okay? So you mentioned the term wavelength a little while ago when we were just sort of going through the frequency or I asked what frequency is. So I know it might seem obvious because the word itself is quite self explanatory, but what does the term wavelength actually refer to and how do we measure the wavelength of a wave? So like from any part of the wave to like any part of the next wave, it's really like I can't really draw it, but Yeah Yeah so it has to be the same part of each wave. So for example, I've chosen two peaks there. The highest point is the peak. Do you know what do we call the lowest point down here? Is it called the off or something? Trough? Yeah, like the dip. So the highest point is the peak and the lowest point is the trough. Now the peak and the trough have the same amplitude of the wave. And so they should be like minor plus two and then minus two. So if this was plus one, plus two, minus one, minus two, my waves at peak are plus two and at trough are minus two. So they have the same amplitude above and below, which is always the case with waves. So you can either measure from two peaks, which I would recommend that you do, because you know, it just makes more sense in terms of being easy to measure the wavelength itself. But if you were going to, you know, if you were going to do something a bit more complex, you just have to make sure that the two points on the adjacent waves are exactly the same. Now, the wavelength measurement should be exactly the same. Okay? The wavelength will be exactly the same no matter where you choose your measurements, as long as you pick two adtwo exact same points on the adjacent waves. So I mentioned it briefly there, but what's the relationship between wavelength and frequency? Wavelengand frequency, I'm pretty sure you said the smaller the wavelength, the bigger the frequency. Yeah. So in terms of like looking at the wavelength and knowing what frequency means, talk me through that. Why would wavelength and frequency be negatively correlated? Why would it be as one goes up, the other goes down, do you think? Shall we look into it? Let's look at a high frequency versus a low frequency wave. So between two identical points on adjacent waves, if wavelength is a distance, what do you think it's measured in? Leave them to the distance. Maybe like, I don't know, millimeters, something smaller than that. Yeah. Interestingly, it's actually measured in meters. Now you're thinking millimeters because obviously they can be very small. But what we end up with doing is saying like times ten to the minus five. So it does end up being a really, really small number. You are right. But then some of them are really long, like radio waves have a really long wavelength. So it's easier to use all in meters. And then we can put times ten to the minus for the ones that have much lower wavelengths. So let's compare a high frequency. I'll just draw them again because I've scribbled over them. But let's compare a high frequency wave to a low frequency wave now. So I'm gonna to do, first of all, high frequency, and then second of all, low frequency. And we're going to talk about why the wavelength is negatively correlated to it. So this is going to be a lower frequency wave. Like this. And this is going to be a much higher frequency wave. They are going to have the same amplitude. But very different frequencies. Okay. So the first wave I've drawn there, the one at the top, what would you say the frequency was? If my graph represents 1s, what would you say the frequency was? Maybe one, two, three, four, five, six, seven, eight, nine, ten and eleven. There's the one at the top first the one at the top three. Well this three point actually is I know it's it's called it's actually 23 quarters about well how many I mean Yeah it would be so in terms of full waves how many other there's two, right? Yeah, Yeah through four Yeah that's one and that's two. So my advice to you would always be choose the peaks and then count between them. And because I think the peaks is just the easiest point to identify on any wave, and it allows us to accurately count the number of full wave cycles that we can see. So the frequency of this is 2 hz, of this wave is 2 hz. What about the one at the bottom then? Oh, one at the bottom is one, two, twelve. Yeah there's twelve waves. How many full waves? Yeah. So one, two, three, four, five, six, seven, eight, nine, ten, eleven. So the frequency of this one is about 11 hz. Okay, so I'm going to use my ruler here. I haven't drawn these very accurately. Obviously mine not perfect, but let's have a look at the wavelength of that first wave at the top there. So in millimeters, what would you say the wavelength of that first one is? The 78 about 50 78. Yeah, I would agree. So let's say the wavelength is equal to 50. Yeah, I go 58 mm. Okay, so 58 mm. Now let's go down here and let's measure one from we're zero now. So zero is there. So zero, where are you zeros there? Okay. So what would the wavelength be of one wave for that one? Thatbe about 1.2. I mean, twelve. Yes, well done. So it's about twelve, isn't it? So where the frequency is much higher, the wavelength is much smaller because with frequency and wavelength have to be negatively correlated. Because if you've got more waves in a short period of time in 1s, the more waves you have in 1s, the closer they have to be together, which makes sense. The less waves you have in 1s, the further apart they're going to be from each other. So the wavelength and the frequency are always negatively correlated, meaning as one goes up, the other one goes down. So let me just type this in and then we're gonna to talk about periods and we're gonna to do the calculation of period frequency in one in a second. So as I'm going to say, yet frequency and wavelength are negatively correlated, okay? This means that as frequency increases, the wavelength of the waves decreases, and vice versa. So if you went the other way around to and vice versa, as frequency increases, the waves are or must be closer together. Closer together. Therefore, wavelength is slower, therefore, wavelength is lower. As frequency decreases, the waves are further apart, therefore, higher wavelength. Sorry, it's just it started to listen to me there. Therefore, this down wavelength. Okay, so higher wavelength. So frequency, remember, I'm sending you a copy of the note too, so you'll have it as well. Okay? So that's why frequency and wavelength are always negatively correlated. So when we look at the electromagnetic spectrum as the final point of today's lesson, you'll notice that the frequency of the waves as we go up, the spectrum starts to increase and the wavelength starts to decrease. So the one at the end has the highest frequency and the lower lowest wavelength, whereas the one at the start has the lowest frequency and the highest wavelength. Okay. So that is frequency and wavelength. We're going to add one more thing in now, which is period akat. Okay, so period or t and this is where we can actually start to calculate the wavelength using the sorry, we can calculate the period using the frequency. So the period of a wave with something we haven't talked about yet, but it's the time taken. So the period of a wave is the time taken for one complete wave to PaaS a point. Period is measured in seconds, is measured in seconds. So let's have a think about this. Okay, let's draw a wave cycle, a wave sequence and oscilloscope. I'm going to put a wave on here. So. Trying to make it as accurate as possible. Okay, now I'm saying my graph represents 1s as I have done with all of the others. So this complete black line represents 1s. It's from zero to one. So what would you say the frequency of this wave was? One, two, three, three ts, 333 quarters ts. Yeah, we'll go with three. We'll go with three. That's fine. Yeah. So we'll go one, two, three. Okay, so we've got three complete wave cycles, so our frequency is 3 hz. So let me write this out. Okay? This wave. Has a frequency of 3 hz. There are three. Full waves. In 1s. Okay. So three full waves in 1s. So then my question is how do we calculate the time of one wave? How do we calculate the time period of one wave? How would you think if you were to. Try and figure it out. So the frequency is three. So there's three waves in 1s. So how are we going to try and work out the time period of one wave? Maybe you calculate it. Yeah how though like how would you do it based on the information you got? You go like 1s. You go like one divide by three. Well done. Exactly. You would you do one divided by three? So you've cracked it there. The formula triangle that we use to link period frequency and one, because the number one represents 1s hertz is measured in waves per second. That's why we use the number one. So to find time or t, which is the time period of one wave, we do one divided by f. And Interestingly, to find f, you do one divided by t. So what we would do is we would do 1s. So we're trying to find t, we would do 1s. Divided by 3 hz, and that's going to give us a time period of 0.3 recurring. And as I said, time is measured in seconds. Okay? So the number of hertz, the number of waves that we see in 1s is three. So each wave must take 0.3, three, three, three, three, three, 3s to complete. Okay? So t one and f is a formula that we've got to be able to use to calculate the time period of any wave. Okay. Let me give you a couple of questions here with this. So the time period. Of a time period of a radio wave is 1.34s. What is the frequency? And then the frequency of a gamma wave is 700 hz. What is the time period of one way? Okay. So just a couple of questions. Yeah, using this form, I have a question. Yeah, sure. There's like garmma wave, like I don't know, a star 's exploding wave. All types of radiation are released by stars, actually, yes, because they're so hot. So gamma radiation will come from stars. Yeah, but so does X -ray radiation and infrared radiation, obviously, light radiation too. Gamma radiation. We are going to talk about this in the last part. This is the last part of waves. And now we're gonna to move on to electromagnetic spectrum. So I'll talk you through that in a sec. So the time period of a radio wave is 1.34. What is the frequency? How would we work it? The. So frequency goes when met the time period of really ways. So one wave is 1.34Yeah. So how many how many waves in a second? Like let me think about twelve. Three, four, three quarter. Well, you've got to do the calculation. If we want to find f, what calculation do we do according to the formula triangle? So time, divide by one. So time equals 1s. Divide by 3 hz. So this will be. So this will be 1.34 divided by. I don't know. So if I say time, I'll rewrite this without the specifics of the last one. If time is equal to one over frequency, what is frequency equal to? 嗯。I don't know, one over time. Okay, so one over time, so let's do it together. So if frequency is equal to one over time, f is equal to one divided by 1.34. Okay? So if you got a calculator you can use or even a phone calculator. Nope. Oh, I haven't got mine either actually. Let's see if I've got a calculator on here. Yeah. Okay, so let's do one divided by 1.34. Was it 1.34? Okay, so the answer is 0.746. 0.746. Now that's frequency. So what's the unit of measurement of frequency? And over m times equals 1s divide by frequency, which is 700 hz. So what's 11, the one that we've just the one that we've just done here, I found out frequency is 0.746. But what's what's frequency measusuring what do I need to put after that number? Herts? Yeah, hurts. Okay, so let's try another one. The frequency of a gamma wave is 700 hz. What is the time period? So how do I calculate the time period? So one divided by some hundred. Yes, excellent. One divided by 700. So let's do that on the calculator. 0.001429. Yeah. So, 0.00, 0.001429. And what would the unit of measurement be if this is the time period? Mm. Thatbe, second, yes. Second, if I wanted to put that number in standard form, how would I do it? What do you mean by that? Do you know how to do standard form? You know when we do times ten to the power of minus three? Oh, yes, remember, but I don't know. Okay, I did. I learned this, but I don't know, with negative numbers. So standard form, standard form is something that we use a lot in physics because obviously we can do large numbers and very small numbers. So with standard form, if you have a negative number, it's always gonna to be times ten to the negative something. Now the first rule of standard form is you have to choose a number between sorry, not choose, but identify the number between one and ten. So identify the number between one and ten. That's going to be your whole number. So identify the number between one to ten. So for us, we have 0.001429. So my number is going to be 1.429. Okay. So I have to somehow work out the difference to that point because my first number has got to be between one and ten. So if I'd have made it 14.2 that wouldn't have worked because 14.2 is not between one and ten. If I'd have made it 0.014 again, wouldn't have worked. Has to be between one and ten. Now I've got to figure out, right, if I say I've gone from 0.0014292, 1.429, how many space is back? Has the decimal point gone? Well, let me have a look. It's here right now. So it's gone one nearly because it's already there. So it's gone 12, right? Yes. So my number is gonna to be 1.429 times ten to the power of minus two because it's gone back. Now a trip with those things is I suppose when we go through the numbers, has it gone back? Minus two? 0.00, 14, 29. Yeah, let's going back two. No, sorry, no, you were right. It is minus three. Sorry, I'm lying. I've done that. That one too big, haven't I? Oh yes, you get the one I skipped the middle one. Yes, sorry, sorry that's completely my fault. I was thinking then it doesn't seem small enough I skip the middle one it's gone from 12, three you were right sorry. So times ten to the power of minus three so the decimal point has moved back three points so it's minus three. Well done. Okay, so that's how we write numbers in standard form with much smaller numbers alright, right okay, we're just gonna to spend the last part talking about something called the electromagnetic spectrum. Now you'll have probably heard of different types of radiation on the electromagnetic spectrum but well have you do you know what the electromagnetic spectrum is? Are you familiar with it? You know? No. Okay, that's absolutely fine. Then I'm going to show you an image you might recognize it though. So here is the electro let's bring this down here is the electromagnetic spectrum. Okay, does it seem at all familiar? Do you recognize any of these names? I know radio waves and microwaves also know light wai know. What do you know about radio waves and niwaves? So radio waves is like from the radio, obviously. So you can like listen to all the song, like all the channel stuff. And I'm I don't really know how it works, but just Yeah, okay. So the electromagnetic spectrum shortened to the em spectrum is the full range. Is the full range of electromagnetic radiation out there. There's nothing else other than this. If it's not on this list, it doesn't exist. So the electromagnetic spectrum is the full range of electromagnetic waves that exist. So they are in order, have a look at the top that shows you the wavelength of the waves. They are in order of decreasing wavelength. So radio waves have a really, really long wavelength. They're really long. So what would you say about the frequency of radio waves? Wait a minute, I have a question. Yeah, sure is. Like this ultra via wave means like the wave you get from the screens. Not from screens from. Think about where does uv radiation come from? I'm racial, the sun mainly. Okay. So do you ever see that you know like when you wear spf like suncream, you get like a uv rating on it? Yeah, that's to protect you from uv radiation because uv radiation is harmful. Okay. So let me just reask my question. If radio waves have a really long wavelength, what would you say about their frequency? Like. 0.5Yeah but you don't have to give me a number. I mean, if they've got a really high wavelength that they've got a low or a high frequency low, yes, because the two are negatively correlated, aren't they? What about gamma rays all the way up the other side? How would you explain the wavelength and the frequency of gamma? So the frequency is really, really, really, really low. Because the wait a minute Yeah the frequency is really really high because there's there's there's basically No This there's not a lot of gap between the wavelengers not really big. Yes, excellent that is it. So the most high frequency wave is gamma and it has the lowest wavelength. I am just gonna to write you out the number it doesn't actually matter. You don't have to learn this but for example, the wavelength of radio waves. So the wavelength of radio waves is above wavelength above 1m radio really? Yeah. So the wavelength of radio waves is over one metre. Okay? So they can actually be up to kilometers long depending on the type and the frequency. The frequency. Of radio waves. Is let me see. Three times ten to the power of eight. Three times ten to the power of eight. Whereas with gamma rays, the wavelength and the frequency of gamma, which are on the other end of the spectrum. So let me have a look at gamma waves. So the wavelength of gamma is 0.01 nm, which is that would be one times ten to the power of minus. So minus nine, minus ten, eleven, minus eleven. I have a question. So that's how how many so how many limeters is like 11 mm? How many how many millimeters? Okay, I'll talk you through that. Give me one sec. So and then gamma rays is in terms of the frequency, it can be one times ten to the power of 19. So a huge amount, right? Let's have a little look at conversion factors. So we have kilometers. We have meters, we have millimeters. I'm not going to do senti because it doesn't fit the pattern. We have micmeters. And we have nanomometers. So kilometers is the biggest, nanometers is the smallest. Okay, now we're going to use ometers as the standard. So if a meter is one, then a kilometer is 1000, right? Because we times one by a thousand. It's a thousand meters. Yeah. So 1m is 1m, a kilometer is a thousand meone millimeter. In fact, let me write that in here like this. So 1m equals 1m. 1m here equals 1 km, even equals a thousand. Meone meter is equal to 0.001 mm. So it's divided by a thousand. Okay? For micrometers, 1m is equal to 0.00. Sorry. Hang on, let me do. I'm just going to put the number in so I don't write it. What wrong? So one, two, three, four, five, micmeters, one micmeters, so it's divided by another thousand to 100000, and then 1m is equal to one, right? One, two, three, four, five, six, seven, eight, one nanometers. Okay. So each time you go down by a thousand, basically, so you go down by a thousand, so divide by a thousand, then you divide by another thousand again, and then you divide by another thousand. So by the time you get to nanometers, 1 nm is a million times smaller than the meters ters. There's 100, there's a million nanometers in a meter. Does that make sense? I have a question. Is any get like more lower? Like like 1 billion something meters equals one? There is. There is definitely there is. Yeah. So there are smaller numbers, but the ones that we come across at key stage three, to be honest, that key stage three, I'd limit us to maybe micrometers. But when you go on to do gcse, we go we talk about all of these, but we don't talk about any bigger or smaller. And if you do, the question would give you the conversion factor. So it doesn't expect you to remember them, but these it expects you to remember. Okay, right. Going back up to the electromagnetic spectrum then. So radio waves are really low frequency and with a really long wavelength. Now they're really not harmful to you at all. However, these three are harmful to you, okay? Ultraviolet, X -ray and gamma rays, these are harmful to humans. Now, have you ever been for an X -ray before at the hospital? So I feel we use like this X -ray stuff to like to see what's wrong with your black friends ins and stuff. I think. Yeah. Have you ever had one though? Yeah, I had like three. Okay. So remember when you went to the hospital, did you go with one of your parents? Yeah. Okay. So where did your parents have to stand whilst you had an x raid on? I think it's like. Some some meters away Yeah in like a side room, usually behind protective glass. Yeah the reason for that is because x rays are harmful. Now the amount of x rays that we get given when we're having our bones tested is really, really, really small. Okay, it's not gonna to hurt you at all, but you need it done. So if you needed to see if your arm was broken, it was a necessity for you to have X -ray radiation passed through. But one of your parents, they don't need the X -ray, so there is no need to expose them to radiation without good reason. So the parents and the radiologist or the person doing the X -ray, they will always stand behind protective glass, because unless it's absolutely necessary, we shouldn't be exposed to harmful radiation. So the first four, radio, micro, infrared and visible, they will not harm you at all. The the last three, they will. So uv radiation, what happens if you go out in the sun without rearing? Uv protection, what you look at the sun? No, no, your skin I'm talking about, at first it wouldn't be it wouldn't be that bad. But like maybe later, like your skin will be like it's you something maybe Yeah and you can get burned as well, can't you? People who go out in the sun too long, they can end up with skin cancer, even like even more dramatically. So these last three are harmful because of the high frequency. So as those types of waves PaaS through your body, they can cause damage to your cells. Okay, they're high frequency, which is what you yes, sure. Go on. So for the microwave, I think my mom told me that if you stand too close to a microwave when it's like working, you'll be like it will be harmful to your body. Yeah, I think everybody's parents have told them that. I've always thought that, but actually microwave radiation is harmless to humans. Now obviously there's always that thought in the back of our minds. Should we reduce the exposure as much as we can though? So it's a bit of a yes and no. The mic standing in front of the microwave is not gonna to make you ill, but maybe we should reduce the radiation that we're exposed to as much as we possibly can even if it is the health healthy type, not healthy I suppose but harmless types of radiation. Okay, so it's like you know I wouldn't stand in front of the microwave. No, but it's not gonna harm you ultimately. Okay, right. Any more questions before we finish? No, but like because my mom told me that every time I used a microwave, I like turn it on and then ran away and like I didn't something I know for something that is something that I was told that as a child too, and don't apparently don't use your phone in front of the microwave. But a lot of these things are just myths. Okay, I'll send you a copy of the note that we've done. Next time we have a lesson, we'll move on to something else. So I'll send you a message and see where you are with biology and chemistry, and we can go on something else, okay? Okay, well done today. I'll see you next time. Okay, bye, Leo. Bye.