# Lesson video

In progress...

Hello.

I am Miss Simkin for those of you who are just joining us and for those of you who might have forgotten my name since last week, that's okay.

I am very excited to be back for your next science lesson.

I hope that you've all had a lovely week, if it's been a week since you've watched the last lesson.

Before we begin, you need to have this equipment.

So you need a piece of paper, a pencil, and a colouring pencil.

The colouring pencil is just if you want to mark your work in a different colour.

Now, there is also going to be a chance for us later in the lesson to do a practical investigation.

And for that, you will need a round and transparent glass of water and a piece of paper.

If you don't have those things, then that's okay.

You can just watch me do the demonstration.

You can still take part in the lesson.

But if you'd like to, you can pause the video and you can go and get what you need now.

In this lesson, we are going to start with our star words like we always do.

Then we're going to do some recap of our last two lessons.

But we're going to look at refraction and then we're going to do an investigation.

And then we are going to quiz ourselves at the end of the lesson and see if after we've learn what refraction is if we can tell the difference between reflection and refraction.

So reflection, we did last lesson, refraction, we're doing this lesson.

We're going to recap reflection before we begin as well.

So our star words today are transparent.

So I'm going to say the word and then it's your turn to say the word.

It's important that we practise these words so we know how to say them.

And then we sound really intelligent if we're ever speaking to someone about science, and also so that we can remember them.

Great.

And the last one, refraction.

Great.

Let's practise that one one more time.

It's our most important word.

This has a refraction, your turn.

Great.

So let's talk about what the underlined words mean.

And then refraction, we will learn about as we go on through the lesson.

So transparent is a descriptive word for a material that we looked at in our first lesson.

And a transparent material is one that lets all the light through.

So a hint is that you can see through transparent materials.

So my water glass here is transparent.

I can see through it and it lets all of the light through it.

It's going to be important for today's lesson.

Reflect, I'm going to do the action.

Can remember what reflect means? Reflect means to bounce off.

So if light is reflected off an object, it bounces off the object.

Well done if you remember that.

And absorb, I'm going to do the action to remind you.

Absorb means to take in.

So do the action and say that with me.

Absorb means to take it.

Absorb means to take it in.

Great.

Let's have a look at our recap section.

So we are experts now on what light is.

if you know what light is, say it to your screen.

Light is a type of energy that travels in a straight line from a light source.

What then is a light source? We've got two examples on our screen.

If you note it, say it out loud.

A light source is an object that emits light.

So the sun and the torch are both light sources on that slide.

So we know already reflection is when light bounces off an often object, and it's light reflecting off objects that allows us to see them.

And last lesson, we looked at reflective and non-reflective materials.

A reflective material, can you remember? You've got some pictures there and a diagram.

Reflective material is one that.

If you know, say that out loud.

Is one that reflects light well.

So most of the light that hits the surface bounces off it.

What then is a non-reflective material? It's the opposite.

So if a reflective material reflects light well, what does a non-reflective material do or not do? If you know, tell your screen.

A non-reflective material does not reflect light well, so sunlight bounces off the object but most of the light is absorbed.

And we looked at two types of reflection.

So we looked at specular reflection and diffuse reflection.

Specular, and they are different because of the direction that the light bounces off them.

I wonder if you can remember, which one bounces in the same direction? We had a tricky way of remembering this, a sticky way of remembering this.

The same direction, which one was that? Was it spectacular or diffuse? If you know, tell your screen.

Great.

It was specular deflection.

So specular reflection is when light all bounces in the same direction.

And diffuse reflection is the opposite.

It's when light bounces in different directions.

Well done if you've got that correct in your pre lesson quiz.

This was our sticky way of remembering, the beginning of the word.

So specular, same direction, smooth surfaces.

Ooh, that's quite fun to say when you emphasise all the Ss.

Say it with me.

Specular, same directions, smooth surfaces.

And then diffuse is different.

Okay.

That's our sticky way of remembering it.

Now this lesson, we are going to look at refraction.

I'm going to show you what refraction is.

For our demonstration today, we only need two things.

It's quite a simple one.

So we need a glass of water and a circular glass is best, and also a transparent glass so that we can see through it, and a pencil.

I'm going to show you something with this pencil.

I want you to watch really carefully what happens when I put it in the water, okay? What can you notice about the pencil? It looks a little bit like my pencil has been chopped in half.

Can you see? Where this waterline is, we have almost like a zigzag.

It looks like my pencil has bent.

I'm going to do it another time.

So you can see my pencil is just a normal pencil.

But, there we go.

As I put it in the water again, it's happened again.

It's zig-zag.

So you can try this at home and you can try moving around your pencil in the water.

Make sure he put it this side down.

If you put it this side down, then you're going to make the lid of the pencil wet.

It's going to be much harder to write with next time.

And see if you can do it yourself.

Can you get your pencil to bend in half? So here's a picture similar to what I just showed you in the demonstration.

We've got our pencil in the water, and we can see that it appears like it's moving in a different direction, like it's separated.

So what's actually going on here? Let's go through it step by step.

So the first thing that happens is light enters the water.

So that's our purple arrow here.

Light is entering the water.

Then when light hits the pencil, it bounces off the pencil.

However, as it bounces, it changes direction slightly.

So if it were to continue in a straight line, it would follow this path, this dotted line.

But it doesn't.

It changes direction.

It follows this pink arrow.

And this is what's called refraction.

So when the light changes direction, we call that refraction.

What do we call it when light changes direction? Refraction.

Great.

And this makes it look as if part of the pencil inside of the water has moved and the pencil has become bent.

It's this change of direction that makes it look like that.

So what's actually happening here? Why does the light change direction? The reason that light changes direction is because it's moving from one transparent material to another.

And at that boundary between the two transparent materials, so in this case, the water and the glass and air are all transparent, at the boundary between the transparent materials, the light changes direction.

And that's because it travels at a different speed through glass and water, which is more dense than it does when it travels through air, which is less dense.

So because that speed is changing, the light changes direction.

So the key thing we need to remember for refraction is that it happens at the boundary between two transparent objects.

So as it moves from one to another, and that this causes it to change directions.

So that gives us our definition of refraction.

When a light wave changes direction as it moves from one transparent material to another.

Okay.

So as it moves from one transparent material to the other, so in this case from water to glass, it changes direction.

Now there are lots of different uses for refraction.

Refraction is used in jewellery making.

It makes jewellery really shiny.

So diamonds are designed in a particular shape before they're put in jewellery so that the light refracts and makes the sparkling effect.

So there's a picture of diamonds.

So you can see they're sparkling.

It can also be used to create coloured white from white light.

We'll look at that more in another lesson.

And it can be used to focus light into a point.

So I have some pictures on the screen that you might have noticed from Toy Story, if you've seen that movie.

And there is not very nice character in Toy Story who gets a magnifying glass and he tries to burn Woody's head.

So he's one of the toys that you can see.

And he uses his magnifying glass to focus the light into one point and put it in a hotspot on Woody's head, which is what you can see in that picture.

So he's using refraction there.

He's focusing it, he's bending the light, he's changing the lights, sorry, direction, so that it focuses in one point on Woody's head.

So those are some uses of refraction.

They can make jewellery sparkle, and they can be used to focus light into one point.

We have some questions now to answer on refraction.

So can you please pause the video and answer these questions on your piece of paper? If you can't quite remember the answers, that's okay.

You can go back to a part in the video and watch them again.

I'm going to make them full screen so you can see them really clearly.

What is refraction? Why does the part of the pencil in the water look bent? And what is one use of refraction? I want you to write full sentences for these answers.

And as always in science, if a diagram will help your explanation, then feel free to draw a diagram as well.

You can now pause the video and answer these questions.

Great.

Now remember, you might have slightly different wording to me.

That's okay, as long as you have the main ideas.

When we're checking our answers, I'd also like you to check your spelling, especially of keywords.

So for number one, you could have written an answer like, when like changes direction as it moves from one transparent material to another.

So that was our definition of refraction.

For number two, you might have written something like, as light moves out of the water and through the glass, it changes direction.

This is called refraction.

I think a key point to have in this answer is that light is going through your two transparent materials and explaining what those are.

So in this case it was our water and then our glass.

And some uses of refraction are making diamonds in jewels sparkle, using a magnifying glass, and to focus light into one point.

For example, in a laser.

Great.

Well done if you've got those.

Just pause the video to give yourself some time to do that now.

The next thing on our list is our refraction investigation.

For this investigation, you will need the following things.

You will need a piece of plain A4 paper, you will need a pencil or a pen, and you're going to need a circular glass of water.

So this is the glass I'm going to use.

You could also use a glass that looks like this or that looks like this.

As long as it's a circular and transparent, that's absolutely fine.

I'm using a slightly wider glass so that hopefully it is easier for you to see what is happening in this experiment.

Okay.

If you are taking part with me, then you need to go and get all of your equipment ready now.

So those three things, glass of water, pencil or pen, and a piece of plain A4 paper.

So pause the video and do that now.

If you don't have those things, that's okay.

You can just watch the demonstration as I go through.

If you're taking part with me, then we're going to go through step by step so you will be able to see exactly what we need to do.

The first thing you're going to do is you're going to take your piece of plain A4 paper, and you're going to draw two arrows on it.

The paper should be landscaped like this, not portrait.

So landscape like this, and both of your arrows need to face the same direction, just like on the picture on the screen.

So here is my example.

Okay.

I've drawn my arrows as different colours just to make it clearer, but it's up to you whether you do that or not.

Make sure they are facing the same direction.

Pause the video to do that now.

Our next step is to take a circular glass and fill it so that it's three quarters full of water.

So about that full, it's fine.

Okay.

If you need to do that now, pause your video and go and get your glass of water.

The next thing you are going to do is this, you need to turn your paper so that it is vertically upright.

So now we're going to turn our piece of people portrait so that, it's not like this.

It's like this.

Okay.

So we're turning our piece of paper portrait like this.

Then your next step is to place the piece of paper so that you can see one of the arrows through the water and the other above the water.

So when I do it for you guys so you can see it on the screen, I'm going to hold my paper like this.

But you will probably want to do it like this.

Like you're hugging a glass of water so that you can see really clearly.

And you're going to try and look through the glass when you do it, okay? Don't do that step yet.

I'm going to show you on the screen first and then you will have a go to do it yourself.

So remember, I'm going to do it this way so you can see, you're going to do it this way so that you can look into your glasses like this, okay? So are you ready? I'm going to put my piece of paper behind my glass and let's see what's going to happen.

So in fact, I'm going to zoom in on it a little bit.

So my arrows are both pointing the same way.

And then I'm going to put it behind my glass.

Can you give me a three second countdown.

Count with me.

Three, two, and one.

Wow! What's happened? Have you noticed? I'm going to move it again so you can see the difference.

My arrows are pointing the same way, and now they're pointing in a different way.

It's not magic.

It's science.

You can now pause the video and have a go yourself.

So what do you think is happening here? Well, the answer is refraction.

Refraction is happening just like when we put our pencil in the water in the demo, refraction is occurring, which is making our image seem different.

It's making the image that we are seeing different.

I would like you now to have a go at answering these questions on your piece of paper.

What did you observe? So what did you see when you did your experiment? And why do you think this has happened? You might want to draw some diagrams in order to help with your explanation here.

If you are drawing diagrams and you're labelling them, remember to use a ruler to draw your label lines.

Pause the video and complete those questions now.

Great.

Well done.

It's time to move on to the next part of our lesson.

Great.

That brings us to the parts of our lesson where we going to be detectives.

And we are going to work out from the pictures that I show you if it is an example of reflection or an example of refraction.

When you're answering the next set of questions and deciding whether something is reflection or refraction, I want you to think about the definitions of reflection and refraction that we've already learnt and include them in your answers.

So, before we start, let's revise our definitions.

So our definition for reflection, is when light bounces off an object.

So this was our action.

The light comes in and it bounces off the object.

Can you show me the action for reflection? Great.

When light hits an object and bounces off it, can you tell me the definition? Reflection is.

Great.

When light hits an object and bounces off it.

Brilliant.

Our definition for refraction is a little bit longer.

The key point is that light is changing direction, okay? So maybe our action could be this.

You can see light coming to a material, and then changing direction like this.

So it's as it passes from one material to another, okay? And that's important.

It's at the boundary of those two materials, two transparent materials that happens.

Okay.

So light's coming in, through and changes direction.

And here the two materials that is passing through are air and let's say this is glass, okay? So at the boundary of the air and the glass, the light changes direction.

Show me the action one more time for refraction.

Great.

Changing direction.

So the full definition for refraction is, when light changes direction as it passes from one transparent object or material to another.

So listen carefully, when light changes direction when it passes from one transparent material to another.

Can you repeat that back to me? When light changes direction, when it passes from one transparent material to another.

Great.

Hopefully that will help it stick in our memories when we look at our questions.

This is a picture.

So for each of these pictures, we need to decide what is happening.

Is it reflection or is it refraction? And then, what I would like you to do is I would like you to write a sentence on your piece of paper or in your book explaining which one you think it is and why.

Okay.

But like I said, we'll do this one together.

So this is a picture I can see.

The first thing I'm going to do is I'm going to look at the picture carefully.

I can see a torch that's labelled light source, I can see the light beam travelling, it's hitting an object and it's bouncing off it.

I used a key word when I was describing the picture, that's already helped me.

I said that light is bouncing off it.

So which one is it? Reflection or refraction? If you know, say it to your screen.

Great.

It's reflection because we know that when light bounces off an object, that is reflection.

So there's a sentence frame down there which you could use to write your answer.

This is reflection because light is bouncing off an object.

So you can pause the video and you can write that answer down now.

Great.

So this is our little memory aid to help us while we're doing this task.

It says reflection equals bounces off and refraction changes directions.

So that's another way to help us remember other than our actions.

For each question, I'm going to ask you to have a go without the memory aid first.

And then if you're struggling, I'll put the memory aid on to help you.

It might be there to start if you need the memory aid.

That's really normal.

And then by the end of it, maybe you can challenge yourself to do it without the memory aid.

Okay.

Have a look at it.

Is this reflection or refraction? When you think you know, you can start writing your answer.

This is.

because.

Is it reflection or is it refraction? Do you think you can do that without the memory prompt? Then you can pause the video and you can start writing now.

If you would like the memory aid, then here you go.

Remember reflection bounces off and refraction changes directions.

I think it's.

because.

When light reflects, it bounces off the object or when light refracts, it changes direction.

Great.

So this was refraction.

Give yourself a tick if you got that correct.

You might remember this from our demo.

I hope you do.

This is refraction because the light is changing direction.

Let's have a look at our next one.

So take a minute to look at the picture.

What do you think it is? Reflection or refraction? If you know, pause and write your answer now.

If you need the memory aid to help you, then here it is.

So this is an example of reflection.

And you can tell because light is bouncing off the mirror.

And so much of the light is bouncing off the mirror in fact that we can see ourselves in the reflection.

The man in the picture can see himself in the reflection.

What is this picture? I want you to look closely.

You've got a boy looking at fish in the water but there's something going on with that light ray.

What's happening? What do you think? Look closely.

There's a dotted line, and then there's a straight line.

What's happened to that line? If you think you know, then you can start writing your answer.

If you want your memory aid, then here it is.

So this is an example of refraction.

Well done if you got that correct.

And you can see that the light is changing direction because it should be following that straight dotted line just like in our diagram with the pencil and the water glass, but the water is causing it to change direction.

So the two objects that it's passing through here, the two transparent objects are the water and then the air.

Okay.

So maybe it would be more correct if I didn't say objects, if I said materials, okay? So first of all, it's passing through the transparent water and then it's passing through the transparent air.

So once it's bounced off the fish, it changes direction.

So the boy is actually seeing the fish in a slightly different place to where it actually is.

Just like what we are seeing the second half of the pencil in that demo in a different place to where it actually is.

So well done if you got that correct.

Here's the next one.

What is happening here? If you need your memory aid, here you go.

Is it bouncing off something? Or is it travelling through and changing direction? The answer here is this is reflection because it's passing through and changing direction, okay? It's not, if it was reflection, it would go like this.

And when it hit that flat light, it would bounce off like this.

It would look like a V-shape.

But instead it's passing through an object and it's not following the straight, it's changing direction.

Well done if you got that correct.

We've got one more example.

What is going on here? I've got some stones on top of a pond or a flat piece of water.

Is it reflection or reflection? If you think you know, write your answer now.

If you need your memory aid, then here it is.

Great.

This is an example of reflection.

We can see the reflection of the stones in the water.

And an answer that you could have written is, this is reflection because the light is bouncing off the surface of the water.

Well done if you've got those correct and well done everybody for having a really good go.

Well done for all your hard work today.

If you are proud of the work that you've completed and you should be, then I would love if you could ask your parents to send me a photo of your work on Twitter.

I will be able to see it if you put the hashtag #LearnwithOak or @OakNational.

Have a lovely, lovely day.

And I will see you back here for our next lesson which will be all about how we are able to see.

It's going to be a good one.

I can't wait.

Bye.