P out. Okay. So last lesson, we were looking at colors and we were looking at splitting light up into the spectrum. Today we're going to cover lenses, the eye and then some basic revision. And then after that, we're going to go on to plant nutrition next lesson. So we're finishing off this topic. Did you have another lesson at school since I saw you last week? Well, had you had it? I never had the lesson. Okay. So do you do sort of exciting things the last few days at school? Yeah. We didn't have like a single lesson. So what did you do instead? We had like a bunch of ascent, please. Yeah. And then we did nothing else. Like feel like watch movies. Yeah, okay. That's that's pretty normal. I think everybody is so tired by that point. They're ready for a rest. Said you have any like Christmas performances? Yeah, we had the pen tool. And. Then it was quite funny and we got like a bunch of sweets. Nice. And what are your hobbies, Linda? Do you do any musical instruments or drama clubs or anything? I do piano, and I play clartte nice. What about art? And then I do some art. Are you good? I don't know. Well, that doesn't matter anyway to think, think I think like I'm good in the class. It's about whether you enjoy it or not. I'd love to be able to draw, but unfortunately, that doesn't come naturally to me. Right, let's look at this homework. So first one, the term used to describe the splitting of light into different colors is dispersion. The color which has been refracted the least is red. Explain why White light splits up into different colors when passed through a prism, right? We have got three Marks. One mark for saying what like is made of different colors. Good, they all refract different amounts. I'm going to give you three mufor that, but we could also mention the frequencies. So remember, frequency is about the speso. This is the important points, the different speeds. So rather than using wavelength, it would be better to use the word frequencies. Explain why a prison must be transparent. To demonstrate this effect, one mark. Yep, otherwise it would be absorbed. Describe a natural phenomenon in which White light naturally spits into different colors. Rainbow, Oh, Oh, yeokay one mark. So for the second mark, you need to say the light is refracted in raindrops. Just going to add that to the bottom there. For that second mark. So you just lost one mark there and put that back on the chat. All right, next one. Light can be reflected, transmitted or absorbed by objects. Describe what happens to light when it is shone on a translucent object, and that is one mark. So the sunlight passes through, but they scatter in different directions rather than straight. Good skettering. We can also put the word diffuse in front of that, but you don't have to have it. Tissue paper correct, transmitted correct describe what happens to light when it is shone on a transparent object. Yeah, PaaS ses straight through again. We can use the word. We want to be more accurate. We can use the word transmitted rather than passes. Just start that in. Give one example of a transparent material. Oliver decides to investigate how much different colors are refracted when they are passed into a rectangular glass block. He shines Green, yellow and blue light at the block at an angle of 30 degrees chd, the angle to the normal at which each color travels. The color of lights is the independent variable angle of refraction, the dependent variable. The angle of incidents perfect Linda welder. Break clearing that off. And let's begin with our lenses. Right, first bit we won't need to do so. We are looking at how lenses, eyes and the pinhole camera work. We're not gonna to do the pinhole camera because you told me youalready done that. So instead of that, we will go on to do some general revision. So we're going to look at the differences between convex and concave lenses. We're going to look at the different parts of the human eye, and then we will compare the eye with a camera. Now skip past this. And I will let you do this next one here. Okay, so spot the mistake. There's the pen. So do you want to correct these diagrams? And just use a different color and just draw the corrected rays on the diagram or whatever you have to do. To make the diagrams correct. What's wrong with the second diagram? Two angles are different. Diagram two or diagram one? Who wait? No. They will be different. The water is denser. It's going from more dense to a less dense. So it bends. Away. From the normal. Got it. Yeah. So that would have been if it was going from air into water, that diagram, wouldn't it? The way that it's drawn there. Yep. Good. Correct. Oh, don't click or you'll get the answers up. Okay, you've done that one anyway. That's all right. Try not to click the last one, right? What's wrong with that? Oh, good girl. Well spotted. So when we draw a plain mirror, we have to do those hash lines. That's it. All next one's. Got it. Wonderful, now we can click the answers. So arrows, always remember to draw your arrows in. To show direction of travel. And because we're going from a less dense to a more dense medium, the ray ends towards the normal. So light gets refracted, so it bends when it moves from one transparent medium to another. But the shape of the material itself can lead to interesting effects. So lenses are made of glass or transparent plastic. Now, if you're talking about little children, quite often their glasses are made of plastic because they are more sturdy. So we're not going to have any cracked lenses if they drop them, not quite so easily anyway. And they will also be cheaper. So glasses do not always literally have glass in them. And they can either be convex or concave, depending on your prescription. Convex, bulge outwards, and then concave. You can remember, think about the word cave. A cave goes into a mountain or a rock. And that can help you to remember that the concave lens bends in. So bulging out at the middle if they're convex, getting thinner in the middle if their concave lenses. Right. I'm just going to check before I go any further whether this is on the worksheet before I go too far. No, not until we get to the eye. That's fine. Yeah, okay. So we can do this next one, right? So look at what happens. So obviously we know light rays travel in a straight line, so they hit the convex lens and then they are bent because of the shape of the lens, and then they all converge. So converge means come together. To a single point, and then the light is focused at the point where the rays converge. Now that's why you have to be careful if you've got a magnifying glass. What type of lens is in a magnifying glass? Convex or concave. Now. That focuses the rays of light to one point, which can be very helpful if you are lost in the woods and you have forgotten to bring a lighter, because you can actually use the rays of the sun. Now, obviously not if it's nitime, but you can use the rays of the sun to start a fire with a magnifying glass. Now that's great, but not so great if you've got a magnifying glass that you have left by your window and you go out for the day because the sun can shine on that magnifying glass and it can start a fire, which has happened in the past. So people have to be very careful, because have you ever seen that you can get like a mirror to do your makeup, that is magnifying. Have you seen those before, Linda? So one side is normal. So these mirrors are for old people who want to do their eye maker but have to take their glasses off. Now if you wear glasses and you've got to take them up to do your eye maup, you're not going to be able to see very well. So that's why these people use magnifying mirrors. But if you leave that in a Sunny spot, you might start a house fire. Have you ever tried to burn something with a magnifying glass? Have you ever done any survival skills? No, it's quite fun. So conx linges can be used to form an image. Now if we follow the points, so if we go from the tip of this tree, when we follow this point here, we will see that the image will be upside down. So why don't we see things upside down? Because their eye is not convex. Okay, well, we'll come on that in a minute. Let's put that in hold. So a convex lens forms an upside down image. Concave this time, so the opposite of converge. Did you use these two words when you did this at scconverge and diverge? No. Okay. Well, we might I'm going to put this on the chat then so that you've got this. Right. Just putting this picture on. Sorry, I'm going to redo that. I've managed to get a red splurge through it. Recall, let's do that again. Linda, do you want to turn your camera off because you keep losing connection? I think you'll get a stronger connection with it off. I keep losing you. Do you turn it off? Oh, wait, wait. I see it. Yeah, just at the top. Okay. That I'd rather you stayed with your camera off and keep losing you. Right? So let's put that one on with the word converge. So converge meaning come together. And then let's put this one on diverge, move apart. No. Right? So concave lenses again, we've got our array of light hitting our concave lens in a straight line, but this time it is bent and the rays spread out. And now we're going to look at the eye. So I'm going to let you do this yourself to see what you can remember. So I think this might be cut and paste. I'll help you. So you'll probably study the eye again in biology. You will find that there be some areas of overlap in science. I'll cut these out, and if you need to resize them, then you can do. And that should be the last one. Okay, you've got the pen Lenser, move them around, resize them if you need to. I would also like you to label. The pupil because that's missing from this diagram. So label that as well. Draw a line and just write the label level bel. You've made a mistake. Something needs moving, okay? Brilliant. Let's go through. So read the label and then read the function, please. Cornea the transparent how to lay yer at the front of the eye that lewipen Lance focuses light onto the retina. Retina retina. Iris the coour part of the eye which controls how much light enters a pupil. Retina the layer at the back of the eye that contains photosensitive cells where light rays are focused. Optic nerve a bundle of nerve fibers that transmit electrical impulses from the eye to the brain. So the cornea, that is the clear outer coating of your eye, which is obviously to protect your eye and stop any dirt or dust getting into your eye. We don't want your eye to be completely open in the sense that things can get inside it. Now sometimes you might get a scratch on your cornea. If something has hit you in the eye that will heal, and of course, nothing important inside has then been damaged. You've then got basically a hole. So the pupil is the round black parts in the middle of your eye, which is a hole, and that's what lets the light PaaS through onto the lens. You've got the iris, which is the colored part, and that is a ring of muscles which can contract to make the pupil bigger or smaller. Now why would that need to happen? Why do we need to control the size of the pupil? I like. It doesn't. He doesn't damage it. Yeah, absolutely. So that's that's one reason. So if your pupils are large, in very bright light, you're going to let a lot of light into your eye and that can damage the retina at the back with these light sensitive cells. Yeah they're quite delicate cells. And if you start damaging those, then you can start to get vision problems. And then of course, the opposite is in dim light. So in dim light, you want your pupil to be very big, to let as much lighin as possible to help you to see better. So the pupil can get larger or smaller to control the amount of light entering the eye, to either protect your eye in bright light or help you to see better in dim light. And then, as I said, the retina at the back, this contains photosensitive cells, is two different types. We've got rods and we've got cones. And that's where the image is formed, on the back of your eye, on the retina. And that image is then changed to electrical impulses, which go to the brain. So just like your eye, your ear, sorry, the auditory nerve changes sound to electrical signals. This changes light to electrical signals. Putting that on the chat. So you got a copy. And in a minute, we can say I'll leave this actually, because we might need this when we compare the eye to a camera. That's just going through what we've just done. Right now, what we said earlier is the lens in your eye convex or Conon cave. And you should have seen from that diagram that we have just done that it is a convex lens. It is bulging outwards. So that means if we go back here. The image that we would have formed on the retina would be upside down. So why don't we see upside down. Any ideas? So the lens in our eye is convex, so the image on the retina is upside down. Because maybe when it gets to our brain, they got switched around. Exactly. That's all that happens. The brain is very clever. That's its job. It flips it the right way for us. That's all. So the retina, the back of your eye, where the image is formed, is made up of two different types of cells, very sensitive, yet they could be damaged by bright light. They are called rods and cones. They are photosynthesis, sorry, not photosynthesis, photosensitive. So they react to light. So photo, Greek word light. The rods are sensitive to very dim light. So when it's dark nighttime, it will be your rods that are helping you to say, well, as the cones are bright light and colso your rods and your cones. So light hitting these cells is converted to an electrical signal sent to your brain by the optic nerve. And that information is then processed, and then the image is flipped the right way up. And we see pretty amazing, really. Yeah p so let's just talk about that bit. So then another adaptation of the lens. Let's go back here. Yeah. So we've got muscles here which are going to change the shape of the lens a little bit to help us to focus. So if these muscles, these muscle fibers, if they contract, what's going to happen to the lens? If it contracts. Are you touching it, Linda? Can you see it? Can you see the picture? Yeah. Yeah. So can you see where I've put two little arrows to those muscle fibers? Yeah. So if they contract, what will happen? The ep the iris the lens will go larger larger Yeah contract means to shorten so if Yeah wait Yeah so it will be pulled that way. So it will get thinner do you agree? Yeah, Yeah. And then if these muscle fibers relax. Yep, relax theyget a bit longer, so your lens is going to go this way. It will get a bit fatter, so we can change the lens in our eye, which will help us to focus. Now we're not going to do that. We don't need to do that. But what we are going to do. Here's this next one. And I'm going to let you see whether you can figure this out yourself. And if you get stuck, we'll look at the PowerPoint to help you. So there's two common types of site problems. So if you are short sighted, that means you can see well up close. So your short sight is good. So you can't see things that are far away. So that's what I have and that's what my glasses are for. So my vision up close is completely fine, but if I look in the distance it's blurry. And this is myopia long sided. Say that again, my left eye is short sidness and my right eye is alongside. Oh my goodness. So you have to have special glasses made. Well, no, because like my right eye is like normal, but like it was long sightedness. But like my left eye is like really short sightedness. So what do you do? Do you have anything to correct that? No. So you get by. Okay. Yeah because my right eye can see clearly. Okay, so it compensates. So then long sighted. So if you are long sited, that means you'll distance vision is good but your close vision is not good. So that's hyperopia. So in both conditions, the problem is due to light not being focused on the retina. So I said the retina is where the image is formed. If your lens isn't forming that image in the right place, then you've got problems. So if you are short sighted, your image is focused before the retina retina, so too soon. But if you are long sighted, your image is focused behind the retina so too far away. So both of these can be corrected with glasses. And then this is going to ask you, so you can scroll up if you need to look at this information. This is going to ask you to think about what type of lenses you need to correct the different problems. And you've got to draw a little diagram. And provide an explanation, right? So have a go at that. Linger. If you get stuck, I'm going to help you. So in this first one here, so this is the problem that I have. So the image is formed here Yeah, rather than here. So in the second diagram, you have got to add a lens, either a convex Yep, or a concave lens. So you're going to draw a lens like one of those, draw your two rays of light again, and then show us where the image will be formed. Yep, so that's good so far. And you're going to need to use the words diverge and converge in your explanations. Now your lens needs to be in front. Think about this. This is either a contact lens or a pair of glasses. They don't go in your eye, thank goodness. Nothat's still in your eye. Got it. That's it. Then draw your two rays of light entering. And then think about what happens with. Okay. Now they're not going to go straight, are they? Should we have some straight lines as we're Yeah, I'd love to see some straight lines. Yeah, okay. Good, okay, add your arrows. You can Yeah, well, you can do your arrows freehand. That's fine. Right now you need to show, are those going to diverge or converge those two rays? They're going to diverge. We probably needed them a little bit closer together. Let's just add those closer together because. Sorry, Linda, to rup your diagram out. They're going to mthe lens all together. Otherwise let's have them put them in the middle more Yeah put them here and then we've got some space, haven't we? Now we've got some space for them to diverge a little bit, but still not completely miss the lens. Wait. So does it like spread out? Yeah, that's it. Exactly that. But now it's going to look exactly the same. So now the lens, because it is a convex lens, it's going to converge them, but they are going to hit the point at the retina. Perfect. That's it. And to add your arrows on again, now we are sorted. So then use the word diverge. And use the word concave lens. Don't tell us about myopia. You need to tell us about why we're using a concave lens. So a concave lens is used, or in your own words. Good. Rebefore they reach the lens. The eyes lens. Or the lens in the eye. Yeah, exactly. That's enough. Put your full stop. Same thing now, but drawing in your Conon vex lens, just draw it slightly further away from the cornea, just to make it a bit easier to get your lines in. You should be able to you go draw a new one. Let's move it back a little bit and we can. Right? And then they're going to converge. So they're not going to touch, but they're going to be a bit close. Don't get them quite so close because remember, your lens has got to converge as well. So just get them in a little bit. And then they've got to continue straight through that set to again, form the image on the back of the retina or on the resonnote in the back of the eye. Got it. Did you do this at school? Lender, no, no. Okay. Well, that's good. We're doing different things. Conand. Conthat's, fine. We're doing different things. That's fine. This is just application of the lenses, isn't it? Which is the type of thing that they're going to ask you in an exam. So use the word converge in this one. Get converges put an s on that. And light before it not they for light before it reaches. Yeah reaches. Yeah and at the top as well. Diverges? Wonderful. I'm going to pop that onto the chat. So you can explain how convex and concave lenses are used to correct short and near sightedness. Now, I think next we're going to compare the camera with the eye, right? So this is what we've just done, right? Camera. So we won't look too much because you've done cameras and you did a pinhole camera, so you did this. So this is what we're going to do now. So add your ticks in to identify which qualities apply to the human eye, the digital camera and the pinhole camera. So which ones have got a lens? I'm just hang on a minute. I think we've cut off I'm going to go to the worksheet because we've cut the bottom off of that. Yeah, that's better. Yeah, that's all of it. So human eye contains a lens so you can tick the first box. They're like a ticthing in the pan, unfortunately not, which is very, very annoying. And I've been moaning about it for years. There is when you do homework marking. So when I edit your homework, they give me a little ticken across there. But for whatever reason, in the toolbar, considering you're teaching and it's something that you would use a lot, I don't know why they haven't done it. One day theydo an update. Did you use a lens in your pinhole camera? No, no. So no lens in the pinhole camera. So that didn't rely on refraction. Yeah inverted image. Yes, good. Good. Yep, the muscles which pull our lens to make it longer or shorter and focus right. Yeah, unfortunately, our eyes can't zoom in. We have to physically move our bodies to zoom in. Then change shape. Yep. And last one, rods and cones. No lens doesn't change shape in a digital camera. You move the lens nearer or further or you have to completely take the lens off and put a different lens on if you want to get one of the real long range lenses. That's it. Brilliant. Well, ter. So that's everything for this. It is double check the PowerPoint. I think we finished, we can go. So I'm going to put this onto the chat for you later. Now some of it you don't need because it's sound as well. And I know you've already done sound in year seven, but I'll put it all on and it summarizes everything that we've done. So wave properties, two different types of waves, superposition, that's where we were looking at water waves, not sound. Obviously you don't need that, not the ear. And then we've got transparent, translucent, opaque reflection, refraction, light lenses and all of the rest of it. So I'll put that on the chat for use if you need to. And let's start with this one. Now some of these might be about sound, but you've studied sound, so you should be able to remember. Tijust thick it, Yep. Correct. Correct. Convex lens. So that's remembering converge and diverge get converge. So come together. Light travels faster. Oh, are you having trouble? You seem to be over the side. You're in trouble getting to the right bit. You can just tell me. Now I'm just looking back on our chat to get you the picture of this because I know this is something that you didn't cover. The. So I Oh, I thought I'd put a picture of this on, but I can't find it. Is it diffuse? It is. Oh, why didn't I put a picture of that on? Not sorry. So specular is when you would have a flat surface, so you would get your reflection like this. So this is specular. And then diffuse is the spreading out all over the place. So if you remember what the word diffusion means, you've covered diffusion. When you're talking about chemistry smells, how smells spread, you done that like the then we've a porgal area. Hi, to low. That's it. So if you think about the word, diffusion means spreading out all over the place. Thathelp, you remember that this is diffuse, spreading all over the place or reflecting all over the place. Let's see what you can remember here. I think we did mention this when we did transverse and longitude and all in the beginning. Yeah which one is it? You can just tell me. In sound waves. Wait, I'm trying to remember what a transfer and longitude in a way of the car. So the transverse is the one that's like this, and then the longitudinal is the one that's got your compressions and rare factions, the squashed bits and the spread out bits. Yeah, it's a long wave. Longitudinal phototo receptors are in there. So this is the rods and the cones retina. Good. This is a sound one again. So air particles travel to the eardrum. Vibration good. Which colors would a magenta filter transmit? Yeah. And in which direction is energy transferred in a longitudinal wave? Parallel. Parallel. That's it. Good. Okay, I will give you some revision homework. I'll put that on the chat later on. And then next lesson, we will start plant nutrition. Okay, Linda, I'll see you next week. Bye bye.