Lesson video

Hello scientist.

My name is Mr. Wilshire.

And in this lesson, we're going to be looking at shadow size.

This is the review stage.

The outcome for this lesson is I can explain results about shadow size.

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

The first is object.

After that, it's shadow.

Then, we have distance, followed by light source.

And finally, results.

Don't worry if you're not too sure what all of these words mean because the definitions are on the screen for you now.

So if you need to, you can pause the video here, have a look at them, and then restart when you're ready to continue.

The first part of this lesson is called reviewing results.

Izzy and Jacob are interested in how an object's shadow can appear to change size.

They know that the height of a shadow, which is how tall it is, has something to do with the object's distance from the light source.

There's Izzy and Jacob.

They have their torch, they have a ruler and the apple as well.

They've carried out a fair test investigation to answer their inquiry question.

Here you can see some images of different size shadows as well.

Jacob says, "Our question is: how does the distance of the object from the light source affect the height of its shadow?" Hmm, were you able to answer this question by looking at some of their answers? Or maybe you've had a go at this experiment yourself.

Scientists will need to make observations and measurements to help them to learn more about the world and how things work.

Architects who design buildings, for example, will also use observations of measurements made by scientists who study shadows to create interesting shapes in their building designs.

Here you can see an image of an architect working very hard, designing some buildings.

There's also some very interesting shadow designs there.

Looks as though that might be inside a very old building, maybe even a church or cathedral, and I can see that there are some shadows forming on the wall there.

So just like shadow scientists, the children made measurements during their investigations.

They measured the height of the object's shadow in centimetres using a ruler.

They measured the distance of the object from the light source in centimetres using a tape measure.

It could have used a ruler as well, but rulers don't always go up beyond 30 centimetres, do they? So in this case, they've used a tape measure to complete their experiment.

They've measured the object each time that it casts a shadow on the wall, and then move the objects a little bit closer or a little bit further away from the light source.

Is this true or false? Scientists make observations and measurements.

The correct answer here is true.

Can we justify our answers at all? Have a look at these statements here.

Is it because they want to use different types of equipment or is it because they want to learn how things work and find out more about the world? The correct answer here is B.

Scientists make observations of measurements because they want to learn how things work and find out more about the world.

Now here are some of the results that Jacob and Izzy collected.

You may remember them.

On the left side of the column there is the distance between torch and apple measured in centimetres and the right column there is the height of the shadow, also measured in centimetres.

Izzy says, "We put the distances between the torch and apple into a logical order.

A logical order means it makes sense.

We put the numbers in order from greatest to least." That's really a numerical order there as well, isn't it? Have you ever done anything similar when you've been ordering something? Have you then found it easier to work with those items because they're in a set order? Izzy says, "What do we do with our results now that we've recorded them in a table?" Jacob says, "We need to review our results to help us decide what happened and explain what we found out." Can you help here? Are you able to offer any suggestions? Have a discussion with the people around you? Restart when you've done that.

How did you get on? Are you able to help the children here? What do we do with our results now that we've recorded them in a table? Hmm, stop and think.

Why do scientists review the results that they've collected? Is it to decide what happened, to explain what they found out or to know how to finish the investigation? The correct answers here is A and B.

Scientists review the results that they've collected to decide what happened and to explain what they found out.

So let's have a look closely at Jacob and Izzy's results.

What do you notice about the numbers in the shadow height column of the table? Hmm, have a discussion.

What do you notice? Restart the video when you've done that.

So what did you pick up on? What do you notice about the numbers in the shadow height column of the table? Well, Izzy here says, "I notice that as the distance side goes down, the height of the shadow goes up." So the closer that the torch gets to the object there, the bigger the shadow becomes.

The shadow gets taller, doesn't it? The children's results show that the shadow gets taller when the distance between the apple and the torch gets shorter.

Jacob says, "Yes, the shadow height was shortest when the apple was furthest away from the torch." Yeah, so there's a very small answer there isn't there? And at the very bottom there, when the torch is very close, it's a much bigger number.

Stop and think.

A shadow will appear larger when the light source and objects are closer together, the light source and objects are further apart or the light source is brighter? The answer here is A, a shadow will appear larger when the light source and objects are closer together.

Here is task A.

Review the results that you have collected.

You're going to need to organise your data in a logical order.

So you could use the results that are on the table here, or hopefully you've got some of your own.

Izzy and Jacob ask, "Does the distance of the object from the light source affect the height of its shadow?" Why don't you decide and prove the answer here by using your data.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? Were you able to review all the results that you've collected? Jacob and Izzy say, "Our results showed that the height of the shadow increased as the distance between the torch and the apple decreased." You can see that in their columns here.

One column there shows a distance between the torch and the apple is getting smaller and the height of the shadow is then getting bigger.

Tells you a lot about how a shadow is formed then, doesn't it? The final part of this lesson is called explaining results.

Jacob and Izzy are fascinated by the results of their fair test investigation.

Izzy says, "Well, I want to explain to other people what we found out and try to explain why." Yes, of course.

Why did this happen? Jacob says, "In a fair test investigation, you need to explain how one thing affects another thing." So by changing that one thing, what is it that you found out? How have you discovered the answer to the question? Jacob says, "Let's remember what the question that we're trying to answer is: How does the distance of the object from the light source affect the height of its shadow?" Here, distance of the object from the light source and the height of its shadow, these are the two things that we're looking here.

Changing one thing affects the other thing.

Are you able to answer this question straight away using some of the knowledge that you've collected? Hmm.

When scientists talk about how one thing affects another thing, they often use words ending in -er to compare them.

And no, they're not just thinking about going, what do I say? No, they're using words that end in -er.

So Jacob completes a comparative sentence to help him to explain his results.

The something, <v ->er the object's distance from the light source,</v> the something, -er the height of its shadow.

How might Jacob complete this sentence using his observations and measurements? What is he going to do? What words is he going to put in there to add that suffix -er at the end? Pause the video and discuss.

Restart when you've done that.

How did you get on? Were you able to choose some good words that you could use at the suffix -er at the end? Let's find out more.

Well, this is Jacob's comparative sentence.

Here you can see another image of observing shadows.

And yes, look, when the torch is closer to the object, the bigger the shadow is.

I wonder if we agree with Jacob here with his sentence.

He says, "The greater the object's distance from the light source, the shorter the shadow." Do we agree with Jacob? Pause the video and discuss.

Restart when you've done that.

So what did you think? Is Jacob correct? Is the greater the object's distance from the light source mean that the shorter the shadow? I think looking at the results and also looking at this image here, I think he's definitely correct, isn't he? If the object is very far away from the light source, then the shadow is going to be a lot shorter, isn't it? If we swap those two words around, you could change it to mean the same thing, couldn't you? The shorter the object's distance from the light source, the greater the shadow.

Look, when the torch is very close, the shadow gets a lot bigger.

Let's stop and think.

When scientists talk about how one thing affects another thing, they often use words ending in -ing to compare them, they often use words ending in -ed to compare them, or they often use words ending in -er to compare them.

What do you think? The correct answer here is that they often use words ending in -er to compare them.

Who do we agree with most here? Do you agree with Sam? She says, "The shorter the distance between an object to the light source, the shorter the shadow." Do you agree with Lucas, "The shorter the distance between an object and a light source, the darker the shadow," or do you agree with Alex, "The shorter the distance between an object and a light source, the taller the shadow"? I think I agree with Alex most there, "The shorter the distance between an object and a light source, the taller the shadow." Izzy and Jacob are trying to explain why the shadow appears taller when the apple is closer to the torch.

Here you can see two images, one 20 centimetres from the torch and another 50 centimetres from the torch.

So what do you think? Why does the shadow appear taller when the apple is closer? Discuss.

So what did you come up with? Were you able to explain it? What is it that happens to the apple that makes a shadow bigger? Jacob says, "Well, I think it's because when the apple is closer to the torch, it blocks more light." Hmm.

Think it could be right there, yes.

And the object is very close to the torch.

It is starting to block a lot more of the light, isn't it? I wonder if you agree with Jacob though.

Pause the video here and discuss.

Restart when you've done that.

So do you, like me, agree with Jacob? Is the apple blocking more light? Let's find out more.

Izzy says, "Yes, I see! When the distance between the apple and the torch is shorter, the shadow is larger." Here you can see two images.

The shorter the distance between the apple and the torch, and then the longer the distance between the apple and the torch.

So the light that is reaching the surface is a lot less when the apple is very far away.

Remember, a light source will create a beam of light, won't it? In this case, the torch has a much more focused beam of light than maybe a lantern or even the sun might do.

So you can clearly experiment and see where that light is heading, and in this case, even block it.

Stop and think.

True or false.

When an object is closer to a light source, it blocks less light.

That makes a smaller shadow.

The correct answer here is false.

Can we justify our answer here? Is it because an object closer to a light source blocks more light and makes a larger shadow? Or is it because an object closer to a light source blocks less light and makes a larger shadow? The correct answer here is A, an object closer to a light source blocks more light.

It makes a larger shadow.

Here is task B.

Look at your own results to answer the question.

Does the distance of the objects from the light source affect the height of its shadow? Use the -er suffix words to help you explain how one thing affects another thing.

Try to explain why this happens using what you've learned about shadow size.

Pause the video here.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? Were you able to use some of those suffix -er words to complete some sentences? Izzy says, "The greater the distance between the light source and the object, the shorter the shadow." Jacob says, "This is because when the object is further away from the light source, it blocks less light, making the shadow appear shorter." Excellent.

So when you've done an investigation of your own, you're then able to write up some comparative sentences, looking at all the different results that you've done, sometimes even using the -er words like you've been using today.

Let's summarise our lesson.

Scientists make observations and measurements.

Scientists review the results that they've collected to decide what happened and explain what they have found out.

We can use words ending in -er to explain how one thing affects another thing.

And when the object is closer to the light source, it blocks more light and this makes a shadow appear larger.

Here you can see a bottle and its shadow.

I wonder if this has confirmed anything that you knew about light and shadows.

And maybe you can have a go creating some shadows of your own.

I'm Mr. Wilshire.

Thank you very much for listening.