Lesson video

Hello, everybody.

It is Miss Simkin, back again for your next science lesson.

So we're going to be thinking today, all about how we're able to see.

For today's lesson, you are going to need the following things.

You're going to need a piece of paper.

You're going to need a pencil, a colouring pencil if you'd like to mark your work in a different colour and a ruler.

We're also going to need these star words today.

So let's start by saying them all, so I'm going to say them, then you're going to say them to your screen.

Transparent, translucent, opaque, eye, brain, signal, and reflect.

Great, some of these words we're already be familiar with, and we're going to go through what they mean before we begin.

So transparent, translucent and opaque, we've learned about before.

Those are ways of describing materials.

So a transparent material lets all the light pass through it.

A translucent material, can you remember how much light does it let pass through it? If you know say it to your screen.

It lets some of the light pass through it.

And an opaque material, how much light? It lets no light pass through it.

Well done if you remember it.

And our next two star words are our eye and our brain.

So those are both organs in our body and they do different jobs for our body.

So our eyes are organs that help us to see.

And our brain is an organ that does lots of things.

It controls our actions.

It helps us learn new things that helps us process information.

So understand information that's coming to us from the environment.

A signal is a type of message, so you might signal to your friend on your play ground or you might signal for them to come over.

It's a type of message.

If I do this, then that's the signal that I want you to come over here.

And reflect, we've loved before, everybody do the action with me.

Reflect, can you remember what it means? It means to bounce off.

Well done.

So, this is what we are going to go through in this lesson.

We are going to recap our previous knowledge like we always do.

Then we're going to go through the steps for how we see, we're going to draw some diagrams and we're going to learn all about the human eye and to finish off, we're going to learn about glasses and sunglasses.

So, let's recap.

Can you remember what the definition of light is? If you can remember these definitions, then say them to your screen.

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

What is a light source then? It's any object that emits light, well done if you remembered those.

We've already spoken about reflection, it's going to be really important in today's lecture, in today's lesson, which is reflection, it's when light bounces off an object.

And then refraction is what we learned about last lesson.

So let's see if we can remember what refraction is.

Refraction is when light changes direction.

So you can see in my picture, the light has changed direction.

It should be following the green light, but it changes and it follows the pink aray.

So refraction is when light changes direction, but why does it change direction? Can you remember? It passes through something.

It passes through two transparent objects.

So it's when a light wave changes directions as it moves from one transparent object to another or as it passes through two transparent objects.

Well done if you remembered that.

Okay, so, I'm going to explain to you how light enables us to see, and I'm going to show you a diagram under my visualizer.

So I'm going to draw you a diagram to explain how we see things.

So we already know, that in order to see things we need light.

So we need to start with a light source.

So let's start with the sun.

Okay, so here's my sun and it's my light source.

Now light rays travel in straight lines from a light source.

We know that light travels in straight lines.

Let's just focus on one of these light rays.

So let's focus on this one.

Now this light ray is going to travel in a straight line, that's not straight.

It's going to travel in a straight line.

And so, it reaches an object.

So this object is an apple.

Once it reaches that object, it's going to bounce off it.

We call that reflection.

So the light ray is going to reflect off the object and it continues travelling in a straight line.

Now, if that light ray were to keep travelling until it reached a person.

So if that person were to get in the way of the light ray then that light ray would travel into their eyes.

So we actually, I'm going to do a close up of the eye.

This part of your eye here, this black circle in the middle is actually a hole and it's called the pupil.

So the light can actually enter the eye of the person through the pupil.

So I'm going to draw my light ray entering the pupil.

Now, once light has entered the pupil, the pupil sends messages to our brain and that's how we see things.

So our first step was a light source produces light.

So that light source could be the sun, it could be a lamp, it could be a tool, but number one, a light source has to produce light.

What happened next? This picture might remind you.

Next, light travelled in a straight line to our object.

So light travels in a straight line from the light source to our object.

So in this example, our object is an apple.

What happened next? If my action didn't give you a hint, then the picture might.

Our next step is that light is reflected off the object.

So first of all, it travels to the object and then it's reflected off the object.

What's step four? What happens after it's reflected off the object? You wonder if this picture will help you remember? So step four, is that the light travels from the object to our eye.

What happens next? There's a picture of an eye here, what's happening in this picture? If you know, say it to your screen, light enters the eye through the pupil.

And then our last step, step six.

See if this picture reminds you, it's the last step.

Our eye sends a signal to our brain.

Well done if you remembered those.

What I would like you to do now is to rewrite these steps.

All six steps are on your screen and I'd like you to rewrite them in the correct order, numbering them one to six.

We're going to make the screen bigger so you can see it really clearly.

I'm going to ask you to pause the video please and complete this task now.

Great, let's see if you were correct.

I bet you got them all right.

Step one, a light source produces light.

Step two, light travels in a straight line from the light source to the object.

Step three, light reflects off the object.

Step four, light travels from the object to our eye.

Step five, light enters the eye through the pupil and step six, our eye sends a signal to our brain.

Well done if you've got those correct.

Give yourself a tick.

If you need some time to correct your answers, no problem, just pause the video and do that now.

The next thing we are going to look at is drawing a diagram.

In science, diagrams are really helpful for explaining things.

Your teacher will often use them to explain things to you, but you can also use diagrams to explain your answers to your teachers.

Diagrams are really, really useful method, okay? So we're going to draw a diagram today to show how we see to help our written art that we've just written down.

So here is an example diagram.

So you can see I've got my light source, I've got my object and I've got my eye.

In this diagram, the arrows show the direction that the light is travelling.

So that arrow goes from light source to object and then object to eye.

Why are my arrows straight? Why do they have to be drawn with a ruler? What do we know about light? Light travels in straight lines.

So for our diagram to be accurate, our arrows have to be nice and straight.

There's something else I could have added to this diagram to make it even better.

I could have added some labels just to make it really clear to anybody who was looking.

So I could have labelled light source, object and eye and I might even have labelled the pupil, which is where light enters the eye.

I'm going to show you another diagram now.

Have a look at it.

What's different about this diagram? Well, my light source is different, this time it's a light bulb and my object is different, this time it's the chair and that's fine, but there's something else that's different about this diagram and in fact, there's something that's incorrect about this diagram.

Can anybody spot the mistake that I have made on purpose? The arrows are pointing the wrong way.

This diagram is saying that light goes from the eye to the object and then back to the light source.

That doesn't make sense.

I don't know anybody who can shoot light out of their eyes, that would be very, very cool, but it doesn't happen, unfortunately.

So this would be the correction.

This way you can see that the arrows are pointing from the light source to the object, to the eye, okay? So make sure that your arrows are pointing the right way when you draw your diagram in a moment.

So I would like you now to draw your diagram.

You can choose a different light source.

You can choose a different object.

That's absolutely fine, but things that you must remember, light rays pointing the correct way.

Light rays drawn with a ruler and make sure your diagram isn't too teeny, teeny tiny, so nobody can see it.

If you'd like to go the extra mile, you can add some labels to your diagram.

Pause the video and do that for me now, please.

Great, I'm sure they're really fantastic.

And I'm excited to see when you send them in later.

It brings us to our next section of the lesson, the human eye.

So we know already that in order to see something, we need light.

We can't see if there's no light because then there's no light bouncing off the objects into our eyes.

So we definitely need light, but we also need our eye.

If we didn't have eyes, we wouldn't be able to see.

If I close my eyes, so I'm now blocking the light from getting in my eye and I no longer see.

Okay, so our eyes are really important organ and they enable us to see, which is one of our five senses.

So the job of the human eye is to take light in from wherever we look and convert that light into signals that are sent to the brain.

This is a diagram of the human eye.

It might look a bit weird to start with, it's as if we took the eyeball and we chopped it in half, okay? So that we can see how the parts of it work.

As we go through this part of the lesson, we'll add our labels and so you can see what each part of the eye is called.

We're going to start with the pupil, which we've talked about already.

So the pupil is the black bit in your eye, okay? It's circular and it's where the light comes into your eye.

It doesn't look like it's a hole because it's covered with other parts of our eyes, but it's actually a hole that light can go into.

This opens up to become very big when more light is needed and it goes small when the light is bright.

So I don't know if you've ever noticed that, but our pupils can change size.

They can go from small to big.

So here is a picture you can see where the pupil is much bigger in the eye.

So have a look and see the difference between them.

You could even try after this lesson doing this yourself.

So if you stand in a dark room or close your eyes for about 60 seconds, maybe two minutes, you could try and see how long it takes.

And then look in the mirror.

You'll see that your pupils have gotten bigger because when it's darker, our pupils get bigger.

And then, if you go and stand in a really light room or stand by the window for a couple of minutes and go back, you'll see that your pupils will have gotten smaller.

So you might want to give that a go and try it yourself.

I will just say one word of warning, please don't look directly into a light source if you're going to try this, it's not safe to put a light, to stare straight into a light bulb.

That would be too much light at once and your poor pupils wouldn't know what to do with that.

Okay, so if you're going to try that yourself, I would use a dark room and a light room, or stand by a window and close your eyes.

So this is where the pupil is on our diagram.

And in fact, let me make it even bigger.

So the pupil, you can see us pointing to that brown bit on the diagram.

So that's because this person has brown eyes and then the hole in the middle is where that light would go through, okay.

Next, we're going to talk about the lens and the cornea.

Let's practise saying those.

Lens, your turn.

Cornea.

Okay, so these parts of the eye allow us to focus the light.

And that means to collect together the light because when light is bouncing off an object, there's going to be lots of light coming at our eyes and we need a way to focus it.

So collect it together into our eye.

This is what a magnifying glass does as well.

So a magnifying glass focuses the light and helps you to see things close up.

So our lens and our cornea acts a little bit like a magnifying glass, or if you've ever used a camera, the lens on a camera focuses the light.

And if your camera isn't focused, your picture will become fuzzy.

So this is where the lens and the cornea are on your diagrams. So they're two different parts.

The cornea is the outer bit of your eye that's curved.

So it's curved like this and it's actually a sticky way of remembering it, okay.

The cornea is curved like the letter C, the cornea is curved.

Another way you can remember is that the cornea covers the eye, okay? The cornea is curved and it covers the eye.

Remember those things and you'll never forget where the cornea is on your diagram.

Then you can see there zoom in, the lens is this part here that looks almost like the glass in a magnifying glass.

You can see it's the same shape, okay? So the lens looks like the glass in the magnifying glass, the cornea covers the eye and is curved.

How do we remember cornea, say it to your screen? Great.

The next part of the eye that we need to talk about is the retina.

Let's practise saying that, retina.

So, we need a way of detecting the light that enters the eye, and this is done by our retina.

So the retina covers the back of our eyes.

So light enters the pupil and just through the pupil is focused by the lens and the cornea.

And then it's detected by the retina on the back of our eye.

The retina is made up of cells that can sense light, and then they change that light energy into an electrical signal.

So that's what our diagram is showing us on the board.

The retina changes light energy into an electrical signal.

It changes what? Light energy into what? An electrical signal.

Okay, that's what our retina does.

Let me show you where the retina is.

So the retina is actually where it's pointing on the diagram, but it covers all of the back of the eye.

So all of that yellow part is the retina.

Those cells are the ones that sense the light that detects the light and they convert it into an electrical signal or an electrical impulse.

The last part we are going to learn about is the optic nerve.

I've put a picture up, so let's read that first.

It says, "Hi brain, you're looking at an apple from the optic nerve," in a messenger symbol.

What do you think the job of the optic nerve might be? So the optic nerve sends the message to our brain.

Okay, that's why we've got a message there saying, hi brain.

And it's telling the brain what we're saying.

So what does the optic nerve send? A message to our brain.

Great, okay, so the retina converts, sorry, senses the light and changes that into an electrical signal, that signal that moves up the optic nerve to the brain, which puts the signal together and gives us a picture of what we are seeing.

This is where your optic nerve is.

It's right at the back and you can see, it starts in the eye and that black and red line will go all the way to our brain, which is pretty cool.

Okay, take a mental picture 'cause I'm about to change the screen and see if you can remember, see if you can label all of the five parts.

So remember cornea covers and is curved.

The lens looks like the magnifying glass.

The retina, I remember it's at the back and another word for back is rear.

So the retina is at the rear of the eye.

Okay, let's see.

Can you remember all of the parts of the eye? Have a go at filling your labels and you don't need to draw the picture, although you can, if you want to, you can just write A and then what the label is for A.

Pause the video and complete that now, please.

Great, let's see if your memories are on fire today.

A was pupil, B was the cornea, C was the lens.

D was the retina and E was the optic nerve.

Well done if you've got those correct, if not, that's okay.

Every time we make a mistake, we learn as long as we correct the mistake, we learn better.

Okay, making mistakes and finding things tricky the first time helps things stay in our long-term memory, which is really important, okay? So we never mind if we make mistakes in this science class.

Your next task is, can you match the part of the eye to its function, to its job? So carries signals from the eye to the brain.

Can you remember which part of the eye carries signals? I'd like you to write it out in a full sentence.

Say that carries signals from the eye to the brain.

The next one says focuses light onto the retina.

A hole through which light enters the eye and cells that sense light and convert it to electrical signals.

Can you please pause the video and complete that task now? Great, let's check your answers.

So the first one was the optic nerve carries signals from the eye to the brain.

The lens and the cornea focus the light and they focus it onto the retina at the back.

The next one is the pupil.

That's the hole through which light enters the eye.

And the last one was the retina, that's the cells that sense light and convert it into electrical signals.

Well done if you've got those correct.

If you made a mistake, no problem, just pause the video and correct your answers now please.

The next part of our lesson is all about glasses and sunglasses.

We use both glasses and sunglasses to help our eyes and to keep them safe.

But we're going to use our learning now of how we see and the parts of the eye to see if we can figure out why glasses and sunglasses work.

Here's a picture of some glasses and you can see somebody is using them to help them read the words.

So some people use glasses to help them see better.

Glasses have lenses that help them to focus the light.

So you can see in this picture, if you look outside the glasses, so around the glass of the big letter F and G, those are not focused.

You can tell because they're fuzzy.

But if you look into the glasses, you can see that the words are focused.

They have really clear edges and they're not fuzzy.

So glasses help us to focus light.

But I have a question for you, which part of the light of the eye are they held? So if we need glasses, which parts of our eyes are they helping? Are they helping the pupil? Are they helping the optic nerve? Think about which part of the eye have we just learned, focuses light.

If you can't remember, check your notes.

It's the lens and the cornea, well done if you figured that out.

So the lens and the cornea are the parts of our eye that focus light.

So if we need glasses to focus light for us, then that means that they they're helping out our lens in our cornea.

If the lens and the cornea that people have in the eye is too strong or too weak, then that's when they might have to have glasses.

So glasses have lenses that add or reduce focus of light to help people to see.

Contact lenses do the same thing.

So you might be somebody who wears glasses or contact lenses.

Let's think now about sunglasses.

Why do we wear sunglasses? When was the last time you wore sunglasses? So we wear sunglasses when it's sunny and why do we wear them? Yeah, they block light from the sun don't they, they stop us squinting when it's really bright outside.

What's the difference between the pair of glasses that I just showed you and the sunglasses.

What's the difference? The difference is the glass, it's of different material, isn't it? It's a different type of glass in each.

In some, in glasses, it's clear glass and here it's dark glass.

I wonder if somebody could use better vocabulary than me to describe the glass clear and dark.

Could we use any of our star words to describe those better? Well, these glasses are transparent.

What about these ones? And why is the glass different? Why do these ones need to be transparent, our normal glasses and why do these not? How do you think about your definitions? So the glass in glasses is transparent because it needs to let all of the light through.

It's important, we need all the light to come through because we want to see all of the light.

But the glass in some glasses is different, it's not transparent.

It doesn't let all of the light through.

In fact, they're specifically designed so that we don't let all of the light through, because remember the job of sunglasses is to block the light.

So the material is not transparent, it's either opaque or translucent.

Why can't they be opaque? Well, if they were opaque, they'd block all the lights and then we wouldn't be able to see the sun, but we also wouldn't be able to see anything.

So that means the glass in sunglasses is translucent.

It lets some of the light in, it lets enough light in so that we can see where we're going, but it blocks some of the light.

So we use sunglasses to block light from the sun.

And this is because the retina, so these cells at the back of our eye that detect light they can be damaged for a short time or even permanently if they receive too much light.

So that's why we shouldn't stare at the sun for example, and why it's a good idea to wear sunglasses when it's a really sunny day.

Well done, if you managed to work that out and spot those differences.

Okay, this is the last question.

We'll ask two questions.

Could you please answer these questions? How do glasses help some people to see? And why is the glass in sunglasses translucent? Please pause the video and answer those questions now.

Brilliant, let's check your answers.

So the first answer was to help them focus light.

You might also have said to help the lens and the cornea to focus light.

Well done if you've got that correct.

Now our second answer.

I've written quite a long answer, or you might have written different words to me.

That's okay as long as you have some of the main ideas down.

So I'm going to read you what I have written.

Translucent materials lets some light pass through them.

Some glasses are made of translucent glass, so that enough light passes through to allow us to see but so sunlight is blocked to protect our eyes.

And then I've written retina to be really specific in brackets, from the sun.

If you need to correct or add anything to your answers, then pause the video and do that now please.

Well done for all your work today.

Just before we finish up and you go and do your post-lesson quiz, let's recap our key vocab.

So transparent materials lets all of the light through.

Translucent materials let most light pass through and opaque materials let no light to pass through.

We learned about why sunglasses and glasses are made of these different materials.

We learned about two organs that allow us to see, our eye and our brain.

So our eye sends this, the information being sent to us and our brain processes that information.

We learned about signals, signals are a type of message.

And we revisited reflection.

Reflection is one of our most important key words in this topic because reflecting light, light that is reflected allows us to see.

Well done for all your hard work today.

Thank you so much for paying such close attention.

Have a really fantastic rest of your day.

And I will see you back here for our next science lesson, which will be all about different colours.

Bye.