Hello, scientists.

My name is Mr. Wilshire, and in this lesson, we're going to be looking at shadow size.

This is the do stage.

The outcome for this lesson is I can measure and record information about shadow size.

As always, there are some keywords for us to remember as we work our way through this lesson.

The first is shadow, then light source, after that distance, then it's measure, and finally, table.

Don't worry if you're not too sure what some of these words mean.

The definitions are on the screen for you now.

So if you need to, you can have a read, remind yourself of them, and then continue when you're ready.

The first part of this lesson is called measuring shadow size.

Izzy and Jacob have been exploring the size of shadows.

Have you ever done this when you've been outside? Have you ever noticed that your shadow is particularly big at certain points in the day? Well, here, you can see that they're playing football, and their shadows have appeared on the ground.

I can also see the outline of, hmm, is it the goalpost there? Or maybe it's a fence that's nearby.

Have you ever looked at the shadows and seen if they are bigger, or smaller at different points in the day? I wonder what time of day this is.

Let's have a think.

What is a shadow? Pause the video here and discuss.

Restart when you've done that.

So what is a shadow? Is it something that you can pick up? Is it something that you can play with? Hmm, let's find out more.

Well, a shadow is formed when light is blocked by another object.

Here, you can see the shadow of a pine cone, and there's also a shadow of a plant.

So the light source is obviously coming from where the photo is being taken.

The item is then blocking the light hitting the wall, and that creates a shadow.

Does a shadow stay where it is once it's been cast, I wonder? Well, Jacob and Izzy have observed that the size of a shadow changes depending on the distance of an object from the light source.

Here, you can see some different size shadows.

Hmm, there's three plant pots.

Oh, it's all the same plant pot, and the shadow looks different.

I wonder how were able to make these shadows change.

So next, they're going to carry out an investigation to find out more.

Wonder, how do you think that these shadows have changed? Stop and think.

Who do you agree with? Aisha says, "The size of a shadow changes "depending on the distance of an object "from the light source." Laura says, "The size of a shadow changes "depending on the size of the light source." Lucas says, "The size of a shadow changes "depending on the brightness of the light source." Hmm, who do we agree with here? Does it matter about the distance, does it matter about the size, or does it matter about the brightness? Pause the video here and discuss.

Restart when you've done that.

Who did you agree with? Well, in this case, I think I agree with Aisha.

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

Izzy and Jacob have chosen the right type of inquiry to investigate shadow size.

Jacob says, "Our question is how does the distance "of the object from the light source "affect the shadow's height?" Izzy says, "Well, we're going to carry out "a fair test investigation to find out." Do you know, do you know how the distance of the object from the light source will affect the shadow's height? Have a think while we go through the next few slides.

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

"This means that only one thing is changed, "and another is measured.

"All other things are kept the same." Izzy says, "The only thing that we are going to change "each time is the distance "between the light source and the object." Okay, so the one thing that's going to change is the distance.

Excellent, then it's a fair test.

If you change too many things, then you won't really be able to compare your answers to anything.

Jacob says, "We're using an apple, because it's opaque.

"It's an opaque object.

"It will cast a dark shadow.

"We'll start with the apple far away from the torch, "and measure the height of the apple's shadow." So there, you can see it laid out in a diagram for you.

It's all labelled, too.

There's the torch, there's the apple, and there's the wall.

Izzy says, "Then we can move the apple nearer to the torch "and measure the height of its shadow each time." So they'll get the torch, get the apple, and they're gonna move the apple each time.

Okay, that's changing one item, isn't it? Jacob says, "Well, we're going to need something "to measure the height of the shadow each time "that we move the apple." Hmm, I wonder what they can use here to measure the height.

Do you know? Pause the video here and discuss.

Restart when you've done that.

So what do you think? How are they going to measure it? Are they gonna measure it with beans, or rope? Hmm, of course, yeah.

They're gonna use a ruler, aren't they? Izzy says, "We can use a ruler, or a tape measure "to measure the height of the shadow in centimetres." Jacob says, "Place the ruler against the wall.

"Start at zero centimetres on the ruler "at the bottom of the shadow.

"Measure up to the top of the shadow to find its height," and that's how tall it is.

So there, you can see the apple is put down on the desk.

There's the top of the shadow there, and the bottom of the shadow is at the zero centimetres part.

Be very careful here if you're going to do this that the ruler that you have does finish at zero.

Otherwise, some of your results may not be quite correct.

Izzy and Jacob check the plan that they have made.

That's really important, isn't it? They've come up with their ideas, so now they need to check.

They need to make sure that their plan is going to be a good one.

Jacob says, "We're using an apple as our object, "because it's opaque and will make a dark shadow "when we shine a light onto it." Izzy says, "I have a head torch that we can use "as the light source.

"If we put them in front of a wall, "if will make it easier for us to observe "and measure the height of the shadow "each time we change the distance of the apple "from the light source." Very good.

I think they thought of everything here, haven't they? So they have made sure that they are measuring the height of the shadow.

They've got the item that they're shining the torch onto.

They've got their light source as well, and they've got a space that they can shine the torch to create that shadow as well.

So the children put everything into place.

There's a ruler, the object, a light source.

They're preparing their investigation.

Izzy said, "Where should I put the apple? "How will I know how far away it is from the head torch?" What do you think? Is anything missing from their investigation? I'm glad that they've stopped to review their plan.

Have a think, pause the video.

Continue when you've done that.

So what did you think of? Is there anything that they've forgotten? Ah.

Jacob says, "We also need to measure the distance "between the apple and the head torch.

"What do you think we could use?" What do you think? So what do you think? What item are they going to use to measure the distance between the apple and the head torch? Well, Izzy says, "Yes, we can measure shorter distances "using a ruler, or longer distances using a tape measure." Ah, so they're gonna use their ruler and they could use a tape measure as well.

Jacob says, "Oh, yes, I see.

"We can place the tape measure on the floor.

"We can measure 50 centimetres away from the torch." Hmm, many rulers don't really go up to 50 centimetres, do they? So it's a good idea to use a tape measure in this case.

Jacob then says, "This is where we will place the apple "to make the first shadow measurement." Excellent, so they've been able to measure everything out.

Izzy says, "Yes, we can use the tape measure, "or a meter-long ruler to help us "to put the apple at different distances "from the light source.

"If we move the apple 10 centimetres each time, we can observe and measure the height of its shadow "to see how tall it is "when the apple is 50, 40, 30, 20, "and 10 centimetres away from the torch." So they're going to move the apple along the tape measure.

Let's stop and think.

What can we use to measure the height of a shadow? Are we going to use a thermometer, are we going to use a ruler, or are we going to use a rain gauge? The correct answer here is a ruler.

That's the best item to use to measure the height of something, in this case, the shadow.

What can we use to measure the distance between the apple and the light source? Weighing scales, a stopwatch, or a tape measure? The correct answer here is a tape measure.

That's the best item to measure the distance between the apple and the light source.

So here's your first task.

You need to carry out your fair test investigation, or Jacob and Izzy's, to answer the question how does the distance of the object from the light source affect the height of its shadow? Here's Izzy and Jacob, and they say, "You could take some photos, "and record the height of the shadow each time." So it's up to you.

Have a go yourself, or use Izzy and Jacob's here.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? How does the distance of the object from the light source affect the height of its shadow? Well, here you can see at 50 centimetres distance it was eight centimetres.

At 40 centimetres distance, it was nine centimetres.

At 40 centimetres distance, it was nine centimetres.

Hmm.

Have we found that there is a difference in the height of the shadow here? What do you think by looking at these answers? Maybe your answers were similar, or if not, hopefully you've been able to view some of these to make your mind up yourself.

Well done.

The second part of this lesson is called recording the size of shadows.

Jacob and Izzy have written their results on a whiteboard.

Jacob says, "Well, we've completed all of our measurements.

"It was all the different height of the shadows, "but now I can't remember what we found out." Here is an example of their whiteboard, 15, 12, eight, 23, and nine.

Izzy says, "Yeah, neither can I.

"Was the shadow 15 centimetres tall "when the torch was 20 centimetres away, "or 30 centimetres away? "I'll check and record the distance "between the apple and the torch, too." Oh, yeah, so that's a good idea.

They need to write down the distance, and then they need to write down the shadow in accordance to that as well, or otherwise, they're not gonna have any idea if they've answered the question about whether the distance of an object from a light source is going to affect the shadow.

Jacob says, "Well, it's very difficult to understand "what our results show when we've recorded "the measurements like this." Izzy says, "Yeah, we need to record our results "in a more organised way, but I'm not sure how." Let's have a quick look again.

So here, you can see they've measured 15, 12, eight, nine, and 23.

Ah, I think that's the height of the shadow, and then the different centimetres that are written down there, that must be the distance.

Hmm, it's not very easy to read at all, is it? So I can see why they're a little bit confused.

I wonder if you have any ideas.

Is there a better way for them to lay any of this out? Pause the video here and discuss.

Restart when you've done that.

How did you get on? Is there another way that they can record this information? Maybe they could write it in sand.

No, that doesn't sound very useful, either.

Well, what they could do is record their results on a table a little bit like this.

Here, you can see one of the headings says the distance between the torch and the apple and in centimetres as well.

Yeah, they certainly weren't measuring in acorns, or snakes, were they? Jacob says, "Yes, in this column, we can put the thing," that's the variable, "that we are changing." Excellent.

Let's stop and think.

Is this true, or false? The results of an investigation can be recorded in a plan.

The correct answer here is false.

Let's justify our answer.

Why do we think this? Is it because the results of an investigation can be recorded in a table, or is it the results of an investigation can be recorded in a prediction? Which of those best match? The correct answer here is a.

Yes, of course, the results of an investigation can be recorded in a table.

So Izzy says, "Well, in this column here, "we can put the height of the apple's shadow.

"This is the that we're measuring." That's another variable as well, isn't it? That's going to change each time, but that's going to be more of an outcome, something that they can measure over time.

So let's stop and think again.

Who do we agree with now? Do we agree with Laura? She says, "A table needs headings for each column "to help people to plan an investigation." Andeep says, "A table needs headings for each column "to help people to make predictions." Alex says, "A table needs headings for each column "to help people to understand the information." Who do we agree with? Why do tables need headings? I think I agree with Alex here.

A table needs headings for each column to help people to understand the information.

Excellent.

It's something that you do as you go, so it's going to help people understand what it is that you found out.

So now that we've got all of that knowledge about tables all wrapped up and ready, let's have a go at Task B.

Step one here is to record Izzy and Jacob's results in a table.

Are their results similar, or different to yours, I wonder? You can record your own results in the second part of this challenge.

So first, have a go at Izzy and Jacob's.

So here is Jacob and Izzy's whiteboard, and some of the parts have already been filled out for you there.

So you need to work out the distances between the torch and the apple and where they go on this table.

I wonder how you're going to organise them in a column.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? Well, here are the answers.

You can see there that we've chosen to put all of the answers in that first column in numerical order, going down from 50 all the way down to 10.

The height of the shadow therefore is changing, isn't it? That is in the right-hand column that goes from eight all the way up to 23.

Izzy says, "I wonder, did your results "look similar to this?" I wonder why they would be different if you're using the same type of materials.

Hmm.

Here's part two.

Use a table to record the results of your own investigation.

Jacob says, "You can use a table like this, "or you could draw your own." Well, you've got your own results now to interpret and put into a table.

So best of luck putting them into the correct columns.

Restart the video when you've done that.

How did you get on? Well, you can see here that there are some other examples for you to look at.

This is from Izzy and Jacob's investigation.

So in one column they put 50 to 10 centimetres, and then in the other column, they were measuring the height of the shadow, and I can see that the distance definitely is having some sort of impact, isn't it? Izzy says, "Are your results similar, or different to ours?" Like I said before, if you were using the same type of apparatus, I wonder if you had similar results.

Maybe if you were using a different object, then you're gonna have a different type of shadow size to this, aren't you? If you were using an apple, I don't know if you'd have exactly the same type of apple as Izzy and Jacob, so your results might be slightly different.

As an extra challenge, you could have a go measuring in centimetres and millimetres as well, so you can really challenge yourself to get an accurate shadow size.

So let's summarise our lesson.

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

Height and distance can be measured using a ruler, or tape measure.

The results of an investigation can be recorded in a table, and a table of results needs headings for each column.

Here, you can see someone measuring shadow size with a torch, a ruler, tape measure, and then apple, of course.

I wonder how you might go on to use some of this shadow knowledge in the future.

Shadows are rather fascinating things, aren't they? And now that you know that there is definitely something that happens when your light source moves nearer to an object, you could have a go at making your own puppet show, maybe.

I've been Mr. Wilshire.

Thank you very much for listening.