Hello, scientists my name is Mr. Wilshire, and in this lesson we are going to be looking at shadow size.

This is the planning stage.

The outcome for this lesson is I can make a plan to investigate how the size of shadows can change.

As always, there are some key words to consider as we work our way through this lesson.

The first is shadow.

Next it's object, then distance, and finally, light source.

Don't worry if you're not too sure what some of these words mean, you can have a look at the definitions that have appeared on the screen for you now.

So if you need to pause a video and discuss, restart when you're ready.

The first part of this lesson is called changes in shadow size.

Jacob and Sofia are playing in the shade under a gazebo on a sunny day.

There's the shade, look underneath the gazebo, which is set up.

Jacob says, "When I'm under the gazebo, I can't see my shadow.

I wonder where it's gone!" Why do you think Jacob and Sofia can't see their shadows when they're inside the gazebo on a sunny day? Have a discussion, restart the video when you've done that.

What did you discuss? Did you think about their sizes of shadows? Is it that they're not standing in the correct place underneath the gazebo? Hmm.

Let's think about it some more.

Sofia says, "We can't make shadows here because we need light to form a shadow, and it's too dark underneath the gazebo." Ah, yes, it is very dark under there, isn't it? Jacob says, "Where could we get the light from?" What do you think? Where could they get the light from in order to make some shadows underneath the gazebo? Have a discussion and restart the video when you've done that.

What did you discuss? Is there a way that they're going to be able to get light in there to make some shadows? Hmm.

Let's find out more.

Well, light comes from a light source.

There's a very big one up in the sky.

It's called the sun.

This is where we get all of our light from on planet Earth.

Without the sun, it wouldn't be warm.

It wouldn't be light.

We wouldn't be able to see things.

Nothing would grow for the sun is a very, very important source of, well, everything.

Sofia says, "We could move from under the shade of the gazebo to where light from the sun is shining on the ground." That's a good idea.

So instead of being underneath the gazebo where they're covered up, they can go outside and they can have a go making some shadows.

The problem there though, is if it's a really hot and sunny day, it might start to burn their skin, and if they're unable to put on sun cream, it would be safer to stay underneath the gazebo, wouldn't it? I wonder if there's another way in which that they could make some light.

Jacob says, well, "Why do we need light for making shadows?" What do you think? Have a discussion and restart the video when you've done that.

So what do you think? Why do we need light for making shadows? What's the point here? You can see a torch.

That's another type of light source.

Although a torch isn't natural like the sun.

It's a manmade source of light, isn't it? So you can turn it off and on as long as it has some charge or some batteries in it, and that will project some light.

So how is it that you can make shadows out of this? Sofia's here to tell us the answer.

"A shadow" she says, "is formed when light is blocked by an object." Here you can see the shade underneath the gazebo.

Yes, I can see the sun on the other side there, and I can see the shade, a great big shadow being cast underneath.

Jacob says, "Ah, yes, I see now gazebos are objects that don't let light travel through them because they're opaque.

The gazebo blocks light from the Sun." That's very true, and opaque objects means that you can't see directly through it.

It will block light from the sun.

If you weren't outside and you were inside, you'd have some light sources, maybe some lights in the ceiling that you could turn off and on again to prove that shadows can be created.

Now, I'm not using lights in my ceiling, but I am using lights to light me up on my camera, which I can turn off like this.

This one here and there, suddenly I've gone a little bit darker.

Now with the other lights, if I cover them up, you can see I turn a little bit darker, and you can also see a shadow of my hand waving around in front of me.

So I can make a shadow using the light sources available to me here.

You don't just need to be able to do this in the sun or with a torch that you're holding.

Let's stop and think.

Who do you agree with here? "Shadows are formed when light passes through an object," says Aisha.

Jun says, "Shadows are formed when heat is blocked by an object." And Sam says, "Shadows are formed when light is blocked by an object." Who do you agree with? Who's correct? Have a discussion and restart the video when you've done that.

Who do we agree with here? Well, we agree with Sam.

She says that, "Shadows are formed when light is blocked by an object." Yes, of course, if you take your hand up to a torch, it's going to cover it up, and then you're not going to be able to see the light coming from the source, are you? Jacob and Sofia go inside to make shadows using the torch and some everyday objects.

Jacob makes a shadow with his pen.

Here you can see a pen and it's shadow.

Sofia says, well, "I'm gonna make a shadow with my pen too." Jacob and Sofia both make shadows.

There you can see Jacob's pen and you can also see Sofia's pen.

Jacob says, "Look! The shadow of my pen is bigger than yours.

Sofia says, well, "I don't understand.

Both of our pens are the same size.

Why is the shadow of your pen so much bigger than mine?" What do you think? Why do you think this is? Have a discussion and restart the video when you've done that.

So why is one pen's shadow so much bigger than the other? What's going on here? Jacob says, "Oh, is it because my torch is brighter than your torch?" Sofia says, "I think it's because we're shining our torches at different distances away from our pens." Well, let's have a look.

If I turn that light source off again, and I can move my hand here and this hand over here, oh, you can see that that size is completely covered up, where there's still a little bit of light coming over here, isn't there? Is it something to do with the distance? What do you think? Stop and think which statement about shadow size is correct? Is it an object shadow is always the same size? An object shadow can change size or the size of a shadow is always the same size as the object? The correct answer here is B, an object shadow can change size.

Does that mean that the shadow does it all by itself? Hmm.

I wonder how that works.

Here is task A.

You need to use some different objects to create some shadows.

How can you make the shadows bigger or smaller, I wonder? Alex says, "You'll need to use a variety of opaque objects such as pencils, toys, and books." Remember, an opaque object is something that you can't see through.

Izzy says, "You'll also need a light source such as a torch, or in this case here you can see that there's a lamp." Well, best of luck with your task.

Have a go making shadows, restart the video when you've done that.

How did you get on? Maybe your findings were similar to this.

Lucas says, "When I moved the light source closer to and further away from the object, I observed that the shadow changed size." There look, you can see some different size shadows, so when the torch got a little bit closer towards it, the shadow would change.

Hmm.

I wonder if you found the same as well.

The second part of this lesson is called planning to investigate shadow size.

Jacob and Sofia use a water bottle to make a shadow.

Here you can see torch close to the bottle and then the torch further away from the bottle.

What do you notice about these two shadows? Have a look at these pictures and discuss, restart when you've done that.

Jacob says, "Sofia is right! The size of the shadow changes depending on the distance of the object from the light source." Did you spot that too? Those shadows are very different, aren't they? One of them is much bigger than the other because the torch is much closer.

Hmm, stop and think.

True or false? The size of a shadow depends on the colour of the object.

The correct answer here is false.

Can we justify that answer? Read both of these statements and decide which one best fits the answer? The correct answer here is A, the size of a shadow depends on the distance of the object from the light source.

It's certainly nothing to do with a colour.

Jacob and Sofia want to investigate shadow size further.

Jacob says, "One way we can measure the size of the shadow is by looking at how tall it is by measuring its height." There you can see the bottle and its shadow, and yes, it is very tall, isn't it? Jacob says, "Our question is, how does the distance of the object from the light source affect the height of its shadow?" Sofia says, "We have our question, but what will we need to do to be able to answer it? Hmm, I don't know.

Do you have any ideas? Have a quick discussion.

Restart the video when you've done that.

I wonder what your ideas were.

What kind of tools are they going to need to use? Are they going to need to use anything specific, or can they use things that they've just got lying around? Scientists do the same kind of thing.

They ask questions and then they plan how to carry out the right type of investigation to find some answers.

Here you can see a scientist planning one such idea for an investigation.

Sofia says, "We need to make a plan for our investigation.

Oh, yes, they will, won't they? So Jacob and Sofia begin to plan what they could do to answer their question about shadow size.

Jacob says, "I have a torch which is a light source, and we can use an apple as an opaque object." Okay, so they can shine their torch onto the apple.

He says, "We can start with the apple far away from the torch and measure the height of its shadow." And Sofia says, "We can then move the apple nearer to the torch and measure the height of its shadow each time." Jacob says, "We'll need something to measure the height of the shadows." Hmm, what can they use here? Discuss.

So what can they use to measure the height of the shadows? Ah, yes, of course, a ruler.

Now, Sofia says, "We can use a ruler to measure the height of each shadow and record our measurements in a table." Ooh, a table.

They're going to need to lay everything out or otherwise it's gonna be a bit messy to look at, isn't it? I wonder if they could decide to change their objects halfway through.

Hmm.

Now, hang on, that wouldn't make it a fair test, would it? You need to keep the same object all the time.

The only thing that they're going to be changing here is a distance away from the torch.

Stop and think.

Scientists ask questions and plan investigations.

Is that true or false? The correct answer here is true.

Let's justify our answer.

Which of these statements best matches the answer? The correct answer here is B.

Scientists plan to carry out the right type of investigation to find answers.

Jacob and Sofia will use their plan to carry out a fair test investigation to find answers to their question.

How does the distance of the objects from the light source affect the height of its shadow? There you can see the apple and the torch that they're going to use.

Jacob says, "We can use our results to find out how changing the object's distance from the light source affects the height of the shadow." There you can see some different height shadows when a torch is being shone onto it.

Then Jacob says, "The size of the shadows must be compared in a fair way.

This means that only one variable or thing is changed and another is measured.

All of the variables are kept the same." Sofia says, "The only variable will change each time is the distance between the light source and the object." Remember, we've talked about this already during this lesson.

They can only change one thing or otherwise it's not going to be a fair test.

Sofia says, "We can move the apple 10 centimetres nearer to the torch each time, and then measure the height of the shadow." There you can see the whole investigation set up for you.

There's the torch, there's the tape measure or the metre length ruler.

There's an apple imposition and there's a ruler for measuring the height of the shadow.

Now, it's really important that the torch and the rulers and other items aren't moved at all or otherwise that's going to affect the test, isn't it? The only thing that's going to be moved each time is the apple.

Stop and think, in a fair test investigation, we keep everything the same.

Is that true or false? The correct answer here is false.

Can we justify our answer? Which of these statements best fits that answer? The correct answer here is B, in a fair test investigation, we change only one thing or variable and measure the other.

Task B now, plan a fair test investigation to answer the question, how does the distance of an object from a light source affect the height of its shadow? Sofia says, "Don't forget to include some information about what you'll need and what you will do!" Ah, yes.

To plan this test properly, you'll need to lay everything out and maybe draw the different items that you're going to need to use.

So best of luck with your planning.

Maybe if you've got some time, you'll be able to run this experiment as well.

Restart the video when you've done that.

How did you get on? Well, here's what Sofia says, Your answer could be similar.

She says, "I'll use an apple as the object and a head torch as the light source.

I'll keep the torch in the same place and only move the apple.

I'll measure the height of the apple's shadow when the apple is 50, 40, 30, 20, and 10 centimetres away from the torch." The things that she's going to need to complete this is a torch, head torch, tape measure, and a ruler.

So there is a Sofia's investigation.

Remember, she's only allowed to change one thing, and that in this case is the apple.

That's the thing that's going to move each time, so she's going to need to be very careful when she's moving things and be very, very accurate to make sure that it is definitely going to be those increments away.

10, 20, 30, 40 and 50 centimetres.

Have a little thing about the answers that she might get.

Is her apple going to have a bigger shadow when it's closer to the torch? Or maybe it'll be bigger when it's further away? I wonder what you think.

Let's summarise our lesson.

Shadows are formed when an object blocks the light from a light source.

The size of a shadow changes depending on the distance of an object from a light source.

Scientists ask questions, then plan how to carry out the right type of investigation to find answers.

A fair test investigation is when only one variable or thing is changed to find the effect on another variable that is measured, all other variables are kept the same.

Hopefully, you've had a good chance to see the different types of experiments that you can do in order to prove the answer to a question.

Remember, when you're testing things, it needs to be fair.

That means that you should only move one item.

Well done for completing the tasks in this lesson.

I'd be Mr. Wilshire.

Thank you very much for listening.