Hello hello can you hear me? Okay Yeah Yeah okay so my name is Katie. I've been you know given the just one sesorry I'm just checking these screens working so we're gonna to do the trial lesson today for obviously your sciences now I've seen a little bit of information about your school reports and so on saying that science is an area of focus and I believe you're in year seven, right? Yeah, Yeah. Okay. So what we're going to do today, Leo, is it's just a trial lesson. So obviously I don't know what material you're currently studying in class or what you've already done. So I've prepared ia lesson on light, hopefully. Have you studied light so far in school? Reflection, refraction, etcec, we're learning light. Oh, that works perfecokay, I didn't actually know that, but that works well. Okay, we'll go through that then. So I'll put some stuff up on the screen. I'll ask you some questions along the way. Don't be worried if you don't know the answer, that's absolutely fine. It's best for me to know that you don't know. Then if you feel like you can't answer, okay, so we're gonna to start with like which is a physics topic within the key stage three science specification. So we're going to talk about how light behaves first of all, okay? So light is a form of energy. It travels in waves. You're probably already aware of the fact that it travels in waves, and it usually travels in straight lines. So when we draw light, we draw light like a straight line like this, and we tend to add the direction arrows to show which way it's travelling. Now this image on the left here is just an image that shows light, and it's trying to really depict how quickly light travels. Now Leo, do you know from class what the speed of light is by any chance? Is it 300000 km per second? Yeah, it's 300 million m ters per second. So you're right. Yes, same thing. Same thing. You've just converted it to kilometers. So it's 300 million m per second. When it travels through a vacuum in, for example, in space, in a vacuum. Now, light doesn't always travel exactly the same speed, because when it travels through different mediums, for example, air or water or solids, even like glass, it can be slowed down, which is the concept of refraction that we are going to look at today. So when we have light traveling through a vacuum, specifically from the sun all the way to planet earth, that is when it's traveling at its fastest and nothing travels faster than the speed of light in a vacuum. What do I mean by vacuum? Leo, do you know? No, there's no there's no like ethere's, no like sounds exactly. There's no particles. Well done. There's absolutely nothing there. So for example, space is a vacuum. There's no air particles, there's no molecules that can slow down or obstruct the movement of light. Okay, well done. So when light hits a material, there really are a few things that can happen. Now this diagram here on the right shows what a few of those options are. So if light hits a reflective material, it will be reflected in a certain way. Although all objects do reflect light, that's how we can see objects, and it's how we can see objects in color as well. So sunlight will be reflected. And that's the first concept that we're going to look at in terms of drawing these ray diagrams. Second option is that some light can be absorbed, meaning that the energy from the light is transferred to the material. Now this often means that that material gets warmer and warmer. So some colors are will absorb more light energy than other colors, for example, black materials. And then other option is that light can be transmitted. So you can see there it says transmission, which means that if you have a translucent or a transsparent material, light can actually PaaS through the substance. Now if I just put here transsparent and translucent, what would you say that an example of a transparent or a translucent material might be? Transpm is a glass. Yeah, well done. And then from lucent is a tracing paper is what? Sorry, tracing paper? Yeah, that's a good one. Actually, I've not had that one being used before as an example. Yeah. So transparent means most of the light can PaaS through, and translucent means that only some of the light can PaaS through. Excellent examples. Well done. And then of course, we have the final option, which is opaque, which would be something like wood, which means that no light can PaaS through. So we cannot see objects on the other side like carbe transmitted through those materials. Okay, great work. So we're going to start with reflection. Then just a brief introduction to how light behaves there. So reflection, as I mentioned, this is the concept of light bouncing off a surface and going in another direction. Now, the concept of reflection is the reason why we can see objects, and also why we can see certain colors, because if an object absorbs certain wavelengths of light, we don't see those wavelengths, and therefore we don't see those colors. But if an object reflects certain wavelengths of light, for example, plants reflect Green light, we then see that object as a certain color. So reflection occurs when light bounces off a surface. But it is a common misconception that this is only reflective. Surface is like a mirror but actually the images formed by a mirror are just really clear images because there are smooth shiny surface. So we end up with specular diffusion of light. So I'm just going to draw a surface here. Okay, so imagine this is a mirror. We are gonna to use a mirror just for the sake of simplicity. So this here is a mirror. Now do you know any rules associated with reflection, Leo? Anything that we need to consider when we are drawing reflection diagrams, you need to put like this on a diagonal line. Yeah. So like this one. Yeah but I thought when mirright like you do like this, some waicon here. Yeah, Yeah. Cause I'll just give you Oh, sorry, I meant to give you the pen. Wrong one. There you go. Yeah, okay. I'm pretty sure it's like this. Oh, Yeah, Yeah, I know what you mean. Yeah to show that it's a reflective surface. Yeah, absolutely. So what I've drawn on here is the incident ray or the ray of incidents, which means that this is the light coming from the source. Now, a source of light is anything that is luminous. So for example, one luminous object or source of natural light is the sun. You can just rub over that. It won't rub out my line because it's Yeah it's because it's a shape. So one source of light is the sun. What are other sources of light? What are other luminous objects? A light like the light you use like that on top. So like electricity. Yep, absolutely. And then there's things like fire candles and even bioaluminescence if we were getting into it. But most of our light comes from the sun or electricity. Most of the light that we come into contact with day to day comes from the sun and electricity. So what I'll do, Leo, is on this diagram. I've just drawn the incident, ray. So say this is coming from the sun or from a light bulb. What do I need to add to this diagram to show how reflection works? You like add a line like Oh that's her you can add it you can you okay, so what's that line you've drawn there? What does that represent? Is the Lila has been reveted yes it's the line of reflection. Well done. I'm just gonna add a straight line in there and why did you draw it at that specific direction and angle because so something like hits it like here about it's basically they put a mirror into it and on top of it and then that just reflects the other way. Yeah so the line that you've drawn is the line of reflection. And do you remember what that White line is in the in ner middle that you've drawn that we call it the. I'm not really sure this is the line of normal or the normal line. So you are absolutely right. It's at a 90 degree angle to the surface, and we draw a line of normal at every point where the incident ray hits the surface. So if I was to add another incident ray and it hits the mirror at a different point, I would draw another line of normal to allow me to calculate what the angle of reflection should be. So the red line is the normal line or the line of normal. It is always at a 90 degree angle to the reflective surface, to whatever the light is bouncing off. And it allows us to predict and determine how the reflective line is going to behave and where we should learn it. Okay, so we've drawn a reflective diagram here. Now there's a rule when it comes to drawing lines of reflection or rays of reflection, and I think you know that rule because you seem to draw the line in the right place. So with reflection, the angle of incidents is here. So the angle of incidents, I'm going to put an eye with the little degree symbol. The angle of incidents represents the angle between the normal line and the ray of incidents. The incident ray. So mine looks to be maybe a bit more than maybe about 50 degrees. Let's say I don't have the protractor on here, so I'm just guessing I'm just sort of eyeboiling it, but let's say it's about 50 degrees. Okay, so what would the angle of reflection have to be and why 50 degrees? Because they have to be like the same. Exactly. So the angle of reflection has to equal the angle of incidents and that is for any instance of reflection. Okay? So anytime reflection occurs off a surface, the angle of incidence is always equal to the angle of reflection and that is the law of reflection as we refer to it. So the angle of reflection is always equal to the angle of incidents. Okay, so the angle of reflection is always equal to the angle of incidents. Now the there are two types of reflection that can occur depending on the type of surface that we have. I'm gonna to show you two images here. So this is one. Notice how they're all abiding by the law of reflection, though. They all have the same angle of incidence as angle of reflection. So these are two different surfaces, okay? The one on the left is a jagged surface, maybe like a rock or something, is Brown. And then the one on the bottom, the one on the right, sorry, is like a mirror. So smooth, shiny surface. You now, what is different about the reflection on each of those images? So for the mirror one, it's all like pretty clear and it just looks the same. And for the left one, the line of incidents all the same, but like the line of reflection just like changing, yes. So because that light is hitting the surface at different angles, because it's not a straight surface. So even though the rays of incident are hitting at the same angle, it seems that the rays of reflection are different angles. But actually it's nice because they are hitting different angles of the surface itself, because the surface is not flat and smooth. So the one on the right hand side of the screen, we call this specular reflection. Now, specular reflection happens when light reflects off a smooth, flat surface, such as a mirror, which is what we've said. This one is metal, for example, or even still water, or that that's quite difficult. So when each beam of light hits the smooth surface and it will strike it at the same angle, because it's from the same light source, and the surface is smooth and flat, and then we see this sort of really neat looking reflective behavior. Now what that means is you're able to see an image really, really clearly. If you're experiencing specular reflection or if you're seeing the results of specular reflection, the image that you see is really, really clear. So for example, if you look in a mirror, you see an image really clearly. You're able to see your features distinctly. But if you were to look on, let's say, into a river, okay, so a river is water. So water is reflective, but it is not a smooth, flat surface. So how does your reflection look when you look at it in a mirror? Like the saying basically, Yeah but how is it different in water? Are you able to see yourself clearly if you look at your reflection in water? A paper, like not clearly. Yeah, not clearly, because that would be an example of diffuse reflection. So this occurs when light reflects off like a rough or uneven surface, or even a moving surface, like water would be, for example. So although the surface might look smooth to the eye at like a microscopic level, it's made up of lots and lots of tiny bumps, or even some movement, which causes irregularities. And when light hits that type of surface, each ray does still obey the law of reflection, like we said. So if we put a normal line in the middle of each of those incident and reflective rays, there will still be the same angle on both sides, but the normal line will be at a different angle at each point, because the surface is uneven. So that's why we can see clear images when we look in a smooth, flat surface that does spececular reflection. But if we look in a rough or unclear surface, we are seeing the results of diffuse reflection. And so the image may not be clear, or we actually may not see an image at all. We may just see the light that is being reflected. And therefore, we're able to see the object, but they're the two different types of reflection that we can have. So reflection is really important, as I said, for allowing us to see objects clearly and just allowing us to see objects at all. Light bounces off surfaces, whether it's a laptop, whether it's an object, whether it's the road outside. Light comes from luminous sources like the sun, like electricity, bounces off the objects and then enters our eye. Now that's the next thing. Okay? So as humans, our eyes are one of our sense organs. Specifically, they sense light. Okay, so I'm going to show you an image of the human eye here. Which part of the eye do you think actually senses light? If you look at the different components of the human eye internally here, blue star, which one? The blue one? See that the light blue one, the lens. Yeah. Okay, so what do you think the lens does? Lungs like reflect it and then make it goes into your eye on assento the brain. Well done. So you're thinking of the term refraction there. Excellent. So I'm just gonna to add in here because that is what the lens does. So the lens refts light entering the human eye and it does allow us to then send messages to our brain. And the brain forms an image. Which part of the eye does the light need to land on in order for us to send a message to the brain? Do you think oya further back into the back of the eye, take the optic nerves going to send the message? I'm just going to put light rays here. So actually, light needs to be refracted onto the retina. Now, this diagram actually makes it quite difficult to refract light onto the retina, but light needs to land onto the retina. The forveyor there is also part of the retina. So as long as light hits our retina, we are able to see it. So when light enters the lens, it is refracted. And tell me, what do you know about refraction? What is the meaning of refraction? Like when the object hit, its something and it just can go through. But like it is light change direction. Yeah, excellent. Yeah. So light is refracted onto the retina. So the lens refts light onto the human eye. The light must be refracted onto the retina because the retina contains what we call photo receptors. So these are specialized little proteins that can detect light. Now, you can't see through anywhere other than your eyes, right? We know that if we lose sight in one of our eyes, we can't pick it up somewhere else. We only have photoreceptors in our retina. So light must enter the eyes. It goes through the cornea, then through the pupil, then it enters the lens that refact it in the right direction. It lands on the retina, and then a message is sent to the brain via the optic nerve. And the brain then formulates an image using the stimulus and the message that has been sent to the brain. So refraction is the next part of this topic, and it's really, really important, particularly when it comes to being able to visualize things and actually see objects around you. It doesn't just start with reflection. We then have to make sure that the light lands in the right place. So you said that refraction is when light passes through an object and it changes direction. Any idea why it would change direction? Because. Arena. So as light passes through transparent or translucent objects, it may be refracted. This means that the light changes direction and may alter the way that an image is seen. So I'm going to give you a little image here that shows, I think it's a pencil. The image I downloaded, Oh, maybe it's not saved on here. So can you think of an example of where refraction makes it look like an object isn't where it actually is? So like how does it make objects seem to be either a different shape or in a different position than they already are? Then they actually are, if you will. I'm just trying to upload this image that I've saved of the pencil. What about if you have you ever dropped something underwater and then you go down to pick it up, but it's not where you thought it was? I did that but where I thought it was okay seems like because what? Sorry, it just sand like it's still like it. Yeah. Okay. So this is what I'm talking about here with the idea refraction. So usually if you do look at something through a dense medium like water or glass, the image is, Yeah, you get what I mean. It's the image is skewed a little bit. So in this case, the pencil looks bent. It looks like it's got a little crook at the bottom, but it actually hasn't. It's just a straight pencil. Now, the reason for this is because as the light passes through the water and then through the air, it's refracted. So the image that we end up seeing is almost like a bit of an optical illusion. It seems like there is a bend, but it's because the light is changing direction. Now the reason light changes direction, so light is refracted as it speeds up or slows down in different mediums. Now there are different mediums. When I refer to different mediums, this means that it depends on the density of the medium. Okay? So the refraction or the way that light is refracted, so the way that light is refracted depends on the density of the medium that it is passing through. What do you think I mean or know that? I mean, by density, it's like how much I had, like how happy like like for example, like cotton if Yeah. So. Yeah so if there's like a little box and you fix and you fit the cotton in it and then you put it on like a don't know, a something that measures the weight I put on it and it would be like five grams. But if you put a box of, if you put metals into the box and fit the box and you put on it, it could be like, I don't know, a kilogram. Yes. I guess how much thing is in like a mesquare meter square cenmestuff? Yes, well done. Because it's a MaaS over volume. So density is calculated using MaaS over volume. So you're right, if we were to have the same size in terms of volume of three different materials, maybe cotton, metal and wood, the actual masses of those materials would be different because of the density of those materials. So having a look at this diagram, this is a very rushed version of the particle model. So on the left you can see the particle model of solids. Then in the middle we've got liquids, and then on the end there we've got gases. So which state of matter has the highest density of the three? Yeah, absolutely. So when light passes through solids such as glass, what do you think happens to the speed of it? Slower, yes, absolutely. And when it gets slower, it slows down. Now, it's not by a significant amount, but there is a noticeable change in the speed of the delight when it travels through different mediums. So light travels fastest in a vacuum because there is nothing there. And in gases, it travels a bit slower in liquids like water, and it travels even slower in solids like gas, for example. And that's why we see this sudden change in direction of light as it passes through these mediums, because its speed changes as it passes through them, meaning that by the time it reaches a sense organ like the eyes, we are perceiving the light at different angles. So we're going na draw a refractive diagram. So I'm just going na write in a couple of rules here before we put the refractive diagram together. So number one, as light passes from a less dense to a more dense medium, for example from air to glass, it slows down. Okay? Then secondly, as light passes from a more dense to a less dense medium, for example, glass to air, so the opposite way now, eg, glass to air, it's beef up. Now what we have to do is how to implement this now into a diagram and determine what angle we think the light is going to travel at in comparison to the incident rate or the refractive rate ay will travel at in comparison to the array of incidents. So I'm going to draw a diagram that initially looks quite similar to a reflective diagram. Okay, now this is the border. Above the blue line is going to be air. Okay? So above the blue line is air and below the blue line is glass. In fact, I'm going to draw the glass as a box because we'll see the, we'll draw the light going all the way through the glass. So a pane of glass like this, so the blue box represents glass. And on both sides of the glass you have air. So right now, if there's a window or anything near you that is transparent, so I'm sitting right in front of a window. If I look outside right now, the air is what's closest to my eyes. But light would have to travel through the glass, through the air on the other side before it reaches my eyes, or it travels through the air, then the glass, then through the air that's closest to me. So it goes through multiple mediums before it actually lands on my retina, which is why the image that I see is probably not indicative of where the object actually is. So we're gonna to start off with the incident, ray, in the same way that we do with reflection, okay? But now we don't use the lore of reflection, okay? We're not using the same angle. What we do need to do though is add a line of normal in there. Now just put this in and then I'll put it in the right place. So you add a line of normal every time your light hits a new surface because you want na figure out which direction the light is going to go in comparison to how it is currently traveling. So this here would just be the angle of incidents. Okay? You already have heard of that one. When we draw reflection diagrams, that is the angle of incidents. But this time we're not drawing the light going off in the opposite direction. The light is actually going to travel through the glass, so it's going to continue forwards. Now remember, as light goes from air to glass, it slows down. So which way do you think away or closer to the line of medium, to the line of normal if it flows down? I think it will be about let me see about. Yeah, well done. So you're right, the light is. Okay, so it was it was a bit blurring for some reason. Oh is it okay again now? Yeah, that's why. Okay, perfect, right? So when a light ray travels from a less dense to a more dense medium, it slows down and therefore it bends towards the line of normal. Okay, so I'm just gonna to type this in here to explain what we've done. So when a ray on light passes from a less dense to a more dense medium, it slows down, which is what we've said above. Therefore. The light ray bends towards the line of normal. So the light ray bends towards the line of normal. The angle of refraction is, what do you think is? Is it higher or lower? Is it bigger or smaller than the angle of incidents? Oh, thanks. Smaller it is. Well, so the angle of reflection, refraction even, is smaller than the angle of incidents. Okay? So that's what happens when we go from air to glass. The angle of incidents. So the angle of refraction is smaller than the just put that than the angle of incidents. Okay? So that's what happens when we go from air to glass. Now I'm just going to make this race smaller so that we can hit it there. Okay. Now as we have a new contact point on the other side, we now have to add another line of normal. So I'm just going to go ahead and add that in here. There we go. Remember, the line of normal always has to be at a 90 degree angle to the surface. So in this case, this is the barrier between the I just can't get that right. Actually, this is the barrier between the glass and the air on the other side, but there's our line of normal. Now this time the light is going to be passing from glass to air. Okay. So is it passing from more dense to less dense or less dense to more dense, do you think? More dense to less dense. It's it's going from more dense to less dense. So how will the speed of light change? Google faster? It will go faster. Well done. So if you've got the ten there, can you just draw a line in where you predict the light will go when it comes out the other side of the glass? Okay. You Yeah well done. So we would say that the light bends away from the line of normal. Now excellent. So let's just add this in here as a straight line. So I'm gonna to add that there. So now we're looking at a different scenario. We're forgetting about the one above and I'm just gonna write in here. So when a ray of light. Passes from a more dense to a less dense medium. It speeds up the light ray, bends away from the line of normal, therefore, the angle of refraction. Is something than the angle of incidents. So in this scenario, what do you think we're going to say about the angle of incidents versus the angle of refraction? Carlike copy it down first. Yeah course you can. Yeah just let me know once you've got that down. And I'll add in, yes, sorry. You just type that, you write that in and just let me know once you've got it in. So in China, when we were like, I don't know, year two or three, which is like the year four or five year, we are like there was like this question, Yeah. So it says, which one is heavier, a kilograms of cotton or kilograms of metal? And then and then the other people le's like, of course it's the metal because like and I'm the smartest persong in our class said, like it depends if the cottton like normal or like water or like because it's wonderful for happy. I was like, it's a kilogram, the same thing. Oh, so did you get it? Yeah, well done. Yeah, that's a classic trick question. I've seen that one many, many times before. But your mind does immediately think, well, it's got to be the metal. But you're right, because it's one kilogram. Obviously, that is the MaaS. Youhave a lot more cotton for a kilogram, but youstill have the same MaaS. So well done. Did you think of that immediately? Yeah, it's like all of kilograms. Well, you're probably one of the few people that didn't get tricked by the question then. Actually, tery, I was the only one. Oh, really? Yes, I've seen that question many times before, and students are always tricked by it, I must say. There's still one more to go. Whereabouts in the light topic have you got two in class so far in class? And the homework we got this week was always a light year and it was like, I'm pretty a light year is about 9 trillion something kilogram a kilometers. Yeah. So tell me, what do you understand about the term light year? What is it there's say light is the speed of the so the light traveling one for one year? Yes, it's the distance that a light would travel in one single year. Why do you think we use light years to measure distance in space? Those are space aces, like really big. Exactly. So if we were going use kilometers or even meters, the numbers that we would use would be huge therebe long standard form numbers to the power of huge numbers. But using light years actually allows us to put it in more feasible perspective, I suppose. So did you have to work out the distance of a light year? The question was, what is the lie? Yer and I explained the speed of life travelfor one year and. And I put like a second line traveling to seconds, 300 thousds about, and I searched up what like years that would be like 9 trillion km. Yeah, I think it's Yeah, I think you're right. I think it's something like 9.5 trillion km. And I put which I put like, which is about what I put, I put like six, I put up 6 trillion miles. Oh, you converted it to miles as well. Yeah. So for the it's like the calculators for like on Google or just like the e plus 20 like something means Oh it's like to the power of it means to the power of so you know when you put like ten to the power of three that comes up as ten three e because they can't the power the Google's Yeah the Google calculator can't necessarily put it to the power of this last sentence is missing a word though. Just be careful because that's what I want us to fill in. When a ray of light passes from a more dense to a less dense medium, it speeds up the light ray bends away from the line of normal. So there's a word missing. The angle of refraction is something then the angle of incidents. Oh, my God, I didn't put the space. I was okay. Just put the little commjust, put this little thing so you can add, add the word in. So. Then. Okay, one array of light passes from a more Bense to a less dense medium. It speed up. It speeds, it speed up. The light ray bends away from the light of normal. The angle of reflfraction is than the angle me instance. Yeah. So do you think the angle of refraction is bigger or smaller than the angle of incidents? Smaller? Well, it was smaller when we went from more, so sorry, from last to I forgot the last our thought the other way around. Bigger. It's bigger. Yeah the angle of refraction is bigger than the angle of incident, right? I'm gonna draw you a diagram now you don't have to copy this in that's fine. You can just do it on the screen. We're going to go from we're going to from water to actually here so this here is going to be water. The blue part of this diagram is gonna to be some water and Yep, go on this refraction, no reason that like when sometimes you go to swimming pool and it's always it's like, Oh, that's really like deep. Not not like deep, but like deep. What's the opposite of deep? Shallow? Yeah shallow. And then you went in there, it's actually really deep. And in the water, when you see see through the water, like for example in the swimming force, the next stairs and the stairs looks like like about that that much in the water, but actually flat, long. Oh Yeah, that's exactly it. Yeah that's why when I said to you at the start, because it's happened to me before, if you drop pped like your goggles or your sunglasses in the water and you look down from on top of the water, they look like they're in one place. And if you reach down, they're actually further to the left or further to the right. But yes, you're absolutely right. The stairs can look smaller or bigger and the surface of the floor can look closer or further away than it actually is, depending on the refraction. Absolutely. Okay. So what I'm going to do here is I'm just gon to let you draw some lines, if you can. You know on the side of your screen, can you choose the straight line option? So you can choose the option where you can use a straight line. It's just easier than to actually draw a raid diagram. I see those taxes. What's this? It's the one with the little pen. Like it looks like a little pen. And if you click on that, you should be able to choose straight line. I don't think I have that. I can really see. No other than I have that I only have, I only have the mouse I have like this and I'm this partner have a rubber and have text. No, that's okay, right? So what I'm gonna do then is I'm drawing a line of normal there for you. That's it. That's all I'm gonna draw. I'm dradrawing a line of normal. What I want you to do is draw a ray of light as it passes through the water and out into the air and show how it would be refracted. So you start your ray of light from inside the water. Okay? So the the ray of light comes from like somewhere here, and you've got to draw it hitting the surface of the water and then going out into the air and you've got to decide, will it be faster or slower? Will it bend away or bend towards the normal line? Okay, so it's like this bit the water right the Yeah the blue bit box is the water. Oh, I'm some. Wait, isn't that like the line alone woman to be like haor something like on top of the water? Well, I'm doing it so that you're going from the water into the air, so it's fine there. So like, okay, sorry, I'm my it goes about here, okay. And then get out of the blood cell. Use your notes as well if you want to, to figure out the rules. Goes like. This Yeah well done. Maybe not so much like that, but it definitely bends away. Yeah, I would agree. Yeah so it bends away from the line of normal and why does that happen? What's happening to the light as it passes from water to air? And there's like less than sense like you, it's faster. Well done. So as the light passes from the water to the air, it goes faster. So let's do this. I'm just gonna to kind of draw depict what you wrote. So the light is traveling in this direction and then as it passes through the water into the air, it speeds up. So can you just label for me the angles of incidents and refraction and tell me which one is gonna to be bigger? So that will be the. Line of incidents this one. Yeah. So that's the line of incidents or the array of incidents. So I'll write that for you, ray of incidents. Yeah. So where would the angle of incidents be? Out here. Yeah, exactly. So then the angle of incidents would be this angle here between the incident ray and the line of normal. And then that's okay, don't worry. And then where would the refraction, the angle of refraction be? The angle for fraction will be sorry about no, no, you're right, but you are right. So this would be the angle of refraction. So remember the angles are always between the normal line and whatever line it is that we automi can do straight lines. Oh, you can do straight lines, right? We'll do one more diagram in a set because I wanted to do another one anyway. So this is the ray of refraction. Okay? And then last example of doing a ray diagram then. So we're going to do, I'm glad you can do that because it's so much easier to use the straight lines to draw ray diagrams. So I'm going to put something here. Okay, so this is a glass. This is glass window. So this is glass window. Above it you have air. Below it you also have air. Now I'm just going to write a little passage here that says light. From the sun, light from an object hits the glass window. Some of it is refracted. I'll put, most of it is refracted. Actually, most of the light is refracted, but some is reflected. Okay, add some lines of reflection and lines of refraction on this diagram. To show how the light behaves. So I'm going to start with the the ray of incidents. Okay, I'm going to start with the ray of incidents. This is going to be the ray of incidents. So that's all I'm gonna to draw on there. So I want you to draw some light being reflected but most of it being refracted and how would the light PaaS through about western line? Yeah, you can power line. Yeah good place to start. Well done. And the line of relax. Okay, remember to put direction arrows on it. Yeah well done and for the. That's you can just I'll extend this normal line for you because you can use the same line of. And you can about like here, that's too much. No, that's fine. That's the upper line. Yeah. It's got to go through both sides of the medium. Oh Yeah so just lift it. Yeah well done. I'll lift it up for you. There you go. I'll delete this one. Hang on there. Yeah Yeah there you go. Right? So your line of normal is there? Okay, well done and leave that but no, I can't know. Sorry. It's okay. Just take your time. You just add your direction arrows into the. I really like use this often. Yeah, that's fine. Don't worry, I stop. Yeah and that's pretty much it. And one more direction arrow needs to be added on one of your rays. Oh well, yes, there you go. Okay, well done. Excellent. That's a really, really good job. Because you've shown the reflection happening at the same angle as the line of incidences hitting the line of normal. Then you've shown that as we go from air to glass, the refracted line travels closer to the line of normal because it slows down. So the angle of refraction is smaller than the angle of incidents. And then on the other side, as the light re emerges from the glass window, you've shown that it's speeding up and the angle of refraction is much larger. Okay, really, really good effort. Well done. That's that's perfect. Actually, just remember that your lines of normal do go through both sides of the medium if we are doing refraction. Okay, well done. Really good effort though. Well done. Okay. Just a last point in class. Have you talked about lenses yet? What lenses, any kind of lens do you recognize the term lens? But from a physics point of view, from from science classes, lens, the objective lenses from the microscope. E, Oh, no, no, that's Yeah. I mean, I know what you mean, but that is a kind of lens, but it's from the microscope. So lenses are transparent objects that refract light in a controlled way to form images. So if somebody, I take it you don't wear glasses because you haven't got any on right now, you don't need to wear glasses, right? Yeah. Yeah. So do you know people who do wear glasses? You will do, won't. Yeah. Why do you think they need to wear glasses? Oh, about that. That's question. I know I'm not sure. So they need to wear glasses because the lens in their eyes don't refract the light properly, and the light doesn't land on their retina. So they can't see. They can't see objects very clearly. So there are two types of lenses that we use in science to correct vision. There are two types. So if somebody has a certain, if they're short sighted, alongsiit, this depends what lens they have. So there are two lenses. One is called a concave lens. The one on the right is a concave lens. So this is a concave lens, and the one on the left is called a convex lens. Okay? Now a convex lens, when light passes through it, it refracts light inwards. Okay? So if I draw two light rays there, if I tell you that the light is refracted even inwards, do you think you could continue both of those lines and show me where you think they're gonna to go? They are referokay through the convex lens thatbe. Like I Yeah Yeah just straight lines though from like from where I've drawn it. So like continue like this if you see what I mean. Yes. Oh, you're drawing the retina. I see. Yeah, well done. That's really good. Yeah, excellent. And then on the concave lens, we also call this a diverging lens. The opposite happens. So light is refracted outwards. So do you think you can finish that one for me? Perfect. Well done. Yeah. So depending on the type of problem that people have with their eyes, they will wear glasses or contact lenses that either contain a convex lens or a concave lens. So sometimes they are unable to refract light enough, so they will wear a convex lens. And sometimes if people's eyes refract light too much, theywear a concave lens to try and correct that. So in your eyes, right? And in my eyes, I don't have to wear glasses either. So both of our eyes have lenses that do the job perfectly. Do you think the lenses in our eyes are convex or concave? They are convex because in the diagram you showed me, it's convex. Well done. It's excellent. Well remembered. They are. So when light passes through our lens, it is refracted inwards at different angles. So sometimes the lens, well, it does. The lens changes shape depending on whether you want to focus on an object nearby or an object far away. So convex lenses are examples like the human eye magnifying glasses as well. And then concave lenses, they are used for corrective measures. So if somebody is over refracting light tends to be if their lens is too thick, then Yeah they they can use a concave lens. Okay, last point, I just wanted to go through with you what you told me about this light year. So when you mentioned for homework that a light year, you were asked to describe what a light year was. Now we already said at the start, didn't we, that light travels at a speed of 300 million m per second. Now what is the relationship between speed, distance and time? How would I calculate distance using speed and time? So b divide by time equals distance. Distance equals wait a minute. So I'm diby by speed equals time. Yeah. So to find distance by by equal speed, Yep. So distance equals speed times time, right? Yeah, Yeah. Because you're right, time equals distance divided by speed. So if you wanted to find out, I mean, I know you googled it. So you know the answer is 9.5 trillion, but how would you work out the distance travelled by light in a year? You already know the you already know it's 300 million m per second. So so how would you work out the time? The time Yeah. So basically the question is how many seconds are there in a year? So it's about a. So ten thousds about a day. So how many seconds are there? How many seconds are there in a minute? So a minute I'll be 60. Yeah. How many minutes in an hour? How many hours in a day? So Oh, 360. 360 times 24 equals something. Yeah. So you work out the number of seconds in a minute times that by the minutes in an hour. So 60 times 60 times that by the hours in a day, times 24 times that by 365. I mean I calculated in the calculator I searched up 300000 because I was using kilters times 60 times 60 times 24 times 365 and I got about nine about 9 trillion. Yeah. So the answer because question is but because Yeah, that's Yeah and then youmultiply those two numbers together. So three, 31 million, 536s thousand seconds times 300 million, that gives you the distance of a light year, which you are right, is 9.5 trillion meand. The reason that we use that measurement is, particularly when we're talking about space, is because it's so vast. So using such a large measurement allows us to kind of put things into a closer perspective. So we could maybe say two light years rather than saying 20 trillion m, which obviously would be a very big number for us to write. Okay, right. This is a really, really great trial. You've done really, really well. You obviously have some good knowledge and you're following the specification well. Is there any questions you want to ask me before we finish anything that didn't make sense or anything you want na ask? No, fine. No. Okay. Did you get everything down that you needed to, that you wanted to? Yeah, okay. I'll send you copies of the images in the chat anyway, so you have those but it was lovely to meet you. Well done and maybe we will see each other again if you sign up for lessons. Okay, have a lovely weekend. Have a loweekend. Okay, bye, bye bye. Thing. I'll shot it now right once day.