Lesson video

Hi, everybody.

My name is Miss Simkin.

I am going to be teaching you science and I absolutely love science.

Our first lesson question, is what is light and where does it come from? So this is the question that we are going to look at today and that we'll be able to answer by the end of the lesson.

So, let's have a look first at what our structure of our lesson today will be.

We are going to look first at sources of light and I've got a demonstration to show you.

Then we're going to look at what reflection is.

Next, we're going to learn about darkness and shadows.

And then we're going to look at materials that are transparent, translucent and opaque.

And then to end the lesson, we have an investigation.

So this is an investigation that you can take part in at home, or if you don't have the equipment that you need, then you can just watch me on the screen do the demonstration and you'll still be able to take apart that way.

So before we begin, let's check that we have everything that we need.

For this lesson, everybody will need a pencil, a ruler, and a piece of paper that can either be a piece of scrap paper or a piece of paper in a notebook or an exercise book that you have.

Great, once you're ready to begin, let's start with sources of light.

So, light is a form of energy that travels in a wave from a source.

A light source is anything that emits light.

So the sun in this example hiding behind my picture is our light source, it emits light.

And the light travels from that source in a straight line.

So light can only travel in straight lines.

There are lots of different types of light sources.

So for example, you could have a torch as a light source.

It emits light.

A match is a light source, stars are light sources.

So in stars, a process called nuclear fusion super heats the particles of gas, making them glow and give off lots of heat and light energy.

And you can even have some animals that are light sources.

See this down here is called a firefly, or a lightning bug, and you can see in it's abdominum over here, it actually glows, it emits light, which is really cool.

I'm going to show you a demonstration now of some different light sources.

It's demonstration time.

But before we start, we're going to need a few things.

So let me go and get them.

This is my special science box.

It is covered in penguins.

A fun fact about penguins is that they don't have any teeth, and so they have to swallow all their food whole.

Imagine swallowing a whole fish.

So let's see what we have in our science box today.

Ah, I can see, we have some different light sources.

So we have some light bulbs, matches, and a candle.

We also have a tennis ball but that's not a light source, that's for later.

Okay, so let's get set up so we can see what these light sources do.

Before we start, I'm actually going to make it a little bit dark in here.

I'm going to turn off the lights and I'm going to close the blinds so that we can see the light being emitted from our light source more easily, and we're not getting interference from the light coming in from the window.

There we go.

So this is our first light source, and this is a match.

So you can see that it is emitting light.

It is glowing.

What's happening here is a chemical reaction between the fuel which in this case is the match and the oxygen in the air.

And that chemical reaction gives off heat and light energy.

And I can use my match to light my candle, which is another light source.

So again, you can see my candle emitting light.

And in this case we have a chemical reaction between the fuel which is the candle wax and the oxygen in the air.

And again, it's giving off heat and light.

So those are two examples of light sources.

Another light source is a light bulb.

So I have two types of light bulb here, and they both work in the same way.

They're not giving off light at the moment and I will explain why.

Inside a light bulb is a small metal wire called a filament.

And when this is actually inside a lamp and it's attached to it's socket and there's electricity going through it, the filament, the little metal wire in the bulb gets hot as the electricity passes through it.

And as it gets hot, it glows and it gives off light just like in, my lamp here.

So here, my light bulb is attached to a lamp and when I click it on, it gives off light.

Okay, back to the lesson.

So when you see this symbol, this means we have a comprehension that we're going to read together.

Now I know that it can be quite hard to read especially if you're use it on a screen especially if it's really small.

So I will read it out loud, and if you want to, you can follow along with your finger or you can just listen.

These comprehensions will normally be a repeat of learning that we've already done as well.

So it's just good to hear it a second time.

And it means that then when you go to answer your questions you can come back to this part of the video if you need a little bit of help.

And you can either listen to it again, or you can read it again.

So let's read our comprehension on light.

Light is a form of energy that travels in a wave from a light source.

Objects that give off light are called sources of light, and they can be described as being luminous.

So the sun is a light source and we can describe it as being luminous because it gives off light.

Examples include, light bulbs, fire, and stars like our sun, and like we just saw in the demonstration.

Each of these objects produce light which moves outwards from the objects in a straight line.

Okay, so that's a really important thing to remember about light.

It always moves in a straight line, okay? So we're now going to have a go at answering our first questions.

You could answer these questions on the piece of paper that you are using.

You don't need to write the question now.

You just need to write the answer.

So the first question is, what is light? The second question is, what are sources of light? So this means the definition, not examples.

So how would you explain what a source of light is? And question three, which word means something that gives off light? If you need some help with these questions then you can go back in the video to the slide where I explain or to the slide where you can see the writing.

When you're ready to answer these questions you can pause the video, and then you can unpause or press play when you're ready to continue on with the lesson.

So if you haven't already, please pause the video now.

Great, once you've finished, let's mark our answers.

You can either use the same pen or pencil that you've been using, or if you have one then it might be nice to mark your answers in a different colour, so that it's really clear.

Here are our answers.

Question one, what is light? Light is a form of energy that travels in a wave from a light source.

Okay, that's our definition for light.

We're going to go back to this definition again and again over this topic.

Question two.

Light sources are objects that give off light.

And question three, the answer was luminous, okay? If you got those answers correct then you can tick your answers.

If you made a mistake, that's okay.

Just correct them and write the answer in that's on the screen now.

It's okay to make mistakes, that's how we learn, and next time you get asked these same questions, I bet you won't make the mistake.

The next thing we are going to look at, is reflection.

So let's look at this diagram to help us explain what reflection is.

We have our light source at the top here, which is the sun.

And we know it's a light source because it's emitting light, it's giving off light.

And then this arrow represents our light travelling from our light source to the object.

Now, remember we learned that light can only travel in straight lines.

So our light is travelling in a straight line from our light source to our object.

When it reaches the object, it bounces off it.

So bounces off it, and we call that reflection.

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

I like to do this action to help me remember what reflection means.

This is my light coming towards my objects, and then it reflects, it bounces off.

See if you can do that action yourself.

And every time you hear me say reflection in this lesson I want you to do the action that will help us remember what reflection means.

Reflection is when light bounces off an object.

Reflection works, a bit like throwing a ball at a wall.

I need to throw my ball at the wall in a straight line and then it bounces off.

So that's what light is doing when it reaches an object.

Sometimes when it reflects off an object, light then reflects into our eyes.

This is what enables us to see.

So these are the steps that allow us to see objects.

Number one, a light source emits light.

Number two, that light travels in a straight line to an object.

Number three, the light reflects off the object.

Well done if you did the action.

And number four, the light reflects into our eyes.

That is how we see.

And then our eyes send messages to our brain.

Let's read our comprehension on reflection.

So you can either read aloud with me or you can just listen to me.

Although light can only move in a straight line, it can bounce off objects that it comes into contact with.

We call this reflection.

Well done if you remembered to do the action.

Lights that bounces off objects and reaches our eye is what enables us to see them.

Sometimes if a lot of light reflects from an object it can look like the object is luminous, but this is not the case.

A good example of this is the moon.

Although the moon can be very bright, it seems as though the moon is giving off light.

It is actually only reflecting light from the sun.

So our sun is a light source that emits light and the moon is not.

The moon looks luminous.

It looks like a light source because it reflects so much light that it looks like it's glowing.

So, can you please answer these questions on your piece of paper? Question one.

How does light move? Question two, what does light do that enables us to see different objects? And three, why is the moon very bright if it's not giving off light? You can pause the video and complete those questions now.

Great, when you're ready, we will mark our answers.

Number one, the correct answer is, light moves in a straight line.

Well done if you copied my hand.

Number two, light bounces or reflects off objects.

And number three, the moon reflects light from the sun.

Give yourself a tick if you got those correct or just correct them with your pencil, if you need to.

The next section we are going to look at is darkness and shadows.

When there is no light somewhere we describe it as being dark.

So darkness is just the absence of light.

If there's no light, then it's dark.

A shadow, is something a little bit different.

So a shadow is created when light from a light source is blocked by an object.

So in this example, the sun is our light source.

It's being blocked by our object, which is a tree, and it's creating a shadow.

Shadows occur because light can only travel in straight lines.

So, it can't go around the tree.

It can't go through the tree.

And so the tree blocks it.

And there's an area behind the tree where no light can reach.

And shadows, because of this often take on the shape of the objects that is blocking them.

So what do you think this is a shadow of? If you know, call it out to your screen.

Yeah, this is a shadow of a dog.

Let's read our comprehension.

When there is little or no light somewhere, we describe the place as being dark.

Darkness is simply the absence of light.

We can have different levels of light to go from complete darkness with no light at all to very bright light, what we might experience on a very sunny day in summer.

A shadow is created when light is blocked across an area to create a patch of darkness and an area that is otherwise light.

We're going to be looking at creating our own shadows later in the lesson.

Can you now answer these questions on your piece of paper? What is darkness? How is a shadow created? You could draw a diagram to help you with this answer if you wanted.

And what object do you think created the shadow in this picture? Pause the video and answer these questions now.

Great, when you're ready, we will mark our answers.

So darkness is the absence of light.

That's our key definition.

A shadow is created when an object blocks light, and that shadow was of a tree.

Well done if you got those questions right.

Give yourself a big tick.

If you made a mistake, that's okay.

No problem, just correct it using the answers on the screen before we move on.

So the next thing we are going to look at is transparent, translucent and opaque materials.

Now, these might be words that you remember or are familiar with, from your science learning in the past especially if you've studied the topic of materials before.

But we are going to recap what they mean because these properties of materials are really important when we're studying light.

So, transparent materials are materials that all light can pass through.

Translucent materials are materials that some light can pass through, and opaque materials are ones that no light can pass through.

So you can see in these diagrams our light source is a torch and you can see the light rays travelling in straight lines to our material.

The transparent one lets all of those light beams through, the translucent one, lets some, and the opaque one lets none through.

So let's have a look at some example materials.

Back to our science box, to see some examples of materials of objects that are transparent, translucent or opaque.

So we're going to test later some of these materials to see how much light passes through them.

That's going to be our investigation at the end of the lesson.

But for now, we're going to just look at them and see if we can tell by observing what kind of material they are.

So, let's start with this.

This cloth is an example of an opaque material.

And I can tell because I can't see through it.

This plastic is an example of a transparent material.

And I can tell because I can see very easily through it.

In fact, if I hold it up to my face, you can still see my face through the material.

So it's transparent.

This is a different type of plastic.

And this is an example of a translucent material.

You can see through it a bit, but not as easily as through transparent materials.

You can see the rough outline shapes, but you can't see them very clearly through it.

So that's translucent.

So we have opaque, transparent and translucent.

Here are our questions for this section.

Can you complete these definitions on your piece of paper? So write a whole sentence out please.

A transparent material is one that, a translucent material is one that, and an opaque material is one that.

Remember, think about the amount of light that they let through.

Pause the video and complete those definitions now.

Great, let's chat our answers.

A transparent material is one that all light passes through.

A translucent material is one that some light passes through.

An opaque material is one that no light passes through.

Give yourself a tick if you've got those correct.

And pause the video if you need some more time to correct your answers before we move on.

Last part of our lesson is an investigation.

We are going to think about the question, how does light behave with transparent, translucent and opaque objects? Now for this section of the lesson, you can either choose to take part, and after you've watched my explanation and my demonstration, you can conduct this investigation yourself.

I will explain the equipment that you need to do that in a moment.

Remember before you start, you always need to check with an adult that they are okay for you to take part in the investigation.

If you don't have the equipment you need or you can't take part in the investigation, that's okay.

You can still take part in the lesson because I will do the investigation on screen.

So you will be able to see exactly what is going on and you'll be able to write the results into your table anyway.

Before we start, I would like you please to draw this table onto your piece of paper.

Op, I just gave you a quick preview of the answers to that hopefully it was too quick for you to see.

So you're going to need to have three columns, and your titles will be object, translucent, transparent or opaque, and what do you observe? Okay, and then you're going to have three rows after your heading row.

For each of these I would leave a good amount of space so that you have the space for lots of notes.

So your whole table, I would suggest should take up about an entire page or maybe three quarters of a page.

Remember that when you're drawing your table that you must use a ruler so that it's really neat, and everybody can read your results.

Please pause the video and get your table set up now.

Great, once your table is ready, we will take a look at our investigation.

You are going to need five things for this experiment.

The first thing that you're going to need is a blank wall or space behind you.

The second thing you are going to need is a light source.

This could be a lamp, this could be a torch, or it could even be the torch on your phone, which is what I am going to use today.

And then the next three things that you need are all materials or objects, okay? I would suggest starting with the same materials that I am going to use, but if you don't have those around or you want to try different materials then that's okay too.

Now I'm going to show you how to set up your experiment.

So the first thing I'm going to do is I'm going to make this room a bit darker.

I'm going to make it light enough so that you can see what I'm doing but dark enough to enable our investigation into shadows to work.

So I'm going to close my blind.

Okay, so, I'm going to demonstrate with a different object.

I'm going to demonstrate first with my tennis ball.

So this is how we are going to investigate the shadows of our objects.

You need to get your light source and turn it on.

You need to direct your light source towards your object and have your object in front of your blank wall like this.

And then you can see the shadow behind it, okay? Could even experiment with different shadow puppets while you're trying to get the best position.

Okay, now we're going to start our investigation and we're going to trial our three objects.

If you want to try this investigation yourself then you can pause the video and have a go now.

Remember to fill in your results in your table because we're going to go through them at the end.

If you'd rather watch me carry out the investigation then I'm going to start now.

So the first object that I am going to look at is my cardboard.

I'm going to hold it between my light source and the wall.

And I'm going to have a look at the shadow.

I can see it's got a really clear outline.

It's taking on the shape of the object and it's a dark colour.

So those are some things that I might write in my table.

I also noticed already, that when I move my object the size of the shadow changes.

So if I move it towards my light source, it gets bigger, and if I move it away from my light source, it gets smaller.

Okay, let's look at our next material.

So I'm going to have a look now at the translucent plastic.

So again, I can see a shadow, it's got a clear outline but it's not as dark as my last shadow.

Let's compare them.

This one was much darker than this one.

And that makes sense because cardboard is opaque.

So it doesn't let any of the light through it, it blocks all of the light, and so my shadow is a dark colour.

But this plastic is translucent.

So it lets some of the light through it, but it blocks some of it, giving me kind of a medium grey shadow.

I'm going to show you the transparent shadow now.

Before I do, have a think, make a prediction.

What do you think the shadow will look like? Let's see if you were correct.

So here's my transparent object.

It barely makes a shadow at all.

Can see an outline, but compared to my opaque object, the shadow is really, really faint.

And that makes sense because transparent objects do let light through, they let all the light through, and so they don't create a very strong shadow.

Let's check if you got similar results to me.

So, for plastic, I thought plastic was transparent because I observed a very faint shadow.

So I could tell that it let all of the light through.

For paper, I put a translucent slash opaque.

It was quite a dark shadow.

So it wasn't letting all of the light through it but it was letting most of it through.

And so I put translucent slash opaque.

And for cardboard, I put opaque, 'cause it was such a clear dark shadow.

I could tell that it was letting none of the light through it.

Well done if you got similar results to me and well done if you tried some different materials.

Let's end our lesson by looking at our star words.

So these were our key pieces of vocabulary that we covered in the lesson.

So before you do your end of lesson quiz, let's go over what each of these words mean.

So, light is a form of energy that travels in a wave from a light source.

And remember we learned that light always travels in straight lines.

A light source is anything that emits light and emits means to give off.

Dark is the absence of light.

A reflection, can you remember the action? A reflection is when light bounces off an object.

A shadow is a dark area where an object has blocked the light.

And then we learned about three different types of material.

An opaque material lets no light through.

A translucent material lets some light through.

And a transparent material lets all the light through.

Well done for today's lesson.

You've worked really, really hard.

Have a go at the end of lesson quiz and I will see you at the same time next week.

I'm already excited.

Have a lovely day.