Hello, scientists.

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

This is the Do and Review stage.

The outcome for this lesson is I can carry out some review and investigation to compare different materials based on how reflective they are.

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

The first is reflect.

Next is surface.

After that is result.

Then, evaluate.

Finally, improvement.

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

The definitions have appeared on the screen for you now.

So, if you need to, you can have a read and remind yourself about what they are.

Pause the video now if you need to do that.

The first section of this lesson is called measuring and recording reflected light.

Alex and Andeep are interested in how light can be reflected.

Hmm.

Have you ever had a go at reflecting light before? What did you use to be able to do it? Alex says, "Well, most materials reflect some light, but some materials are more reflective than others." Andeep says, "I want to compare how reflective different materials are." Hmm.

Can you explain to a partner what it means when light is reflected? Have a go discussing this now.

Restart the video when you've done that.

How did you get on? Were you able to explain to your partner what it means when light is reflected? When light is shone onto something, does it immediately bounce off? Hmm, let's find out more.

Reflection involves a source of light and a surface.

Alex says, "When light reaches a surface which it can't pass through, it can sometimes bounce, or reflect off the surface." Here, you can see the light source, and it's shining a light onto a surface.

You can see that the light is following the arrow, getting to the surface, and bouncing off of it.

This is the light reflected by the surface.

Have you ever seen this before when you are at home? Have you ever used a torch in this way? Usually, the surface in question would need to be reflective, wouldn't it? So, an item would need to shine onto it and then be reflected back off of it.

Not all items have a surface that is particularly reflective.

So I wonder what kind of things that Alex has been shining his torch on here.

Reflective materials are one example of these items. They can help to keep us safe.

Streetlights reflect off the surfaces of some types of clothing, and wow, look, it's like they're wearing a giant torch, isn't it? Car lights reflect off the surface of materials attached to bicycle wheels.

Oh, you can see those little orange reflective discs there.

They can reflect the light off of a car, so that somebody is aware that there's a bike there.

Sometimes, it can be very difficult to see cyclists, so I'm glad that there are reflective surfaces on bikes.

Ooh, in fact, I can see that there's also another reflective red surface on the very back of the seat.

Can you see it as well? Two great example of reflective materials there.

The orange and red plastic items on the bike and some amazing reflective clothing being worn to keep me safe and seen.

Reflective materials can also warn us of dangers by helping us to see objects when it's dark and the light shines on them.

Just like these traffic cones.

Usually, traffic cones are quite a dark colour, even though they're orange, but they're obviously wrapped in some sort of reflective material.

That makes them stand out, it really makes them shine in the car headlights.

I can see as well that there's a white van on the side there, and that's also got a some sort of reflective yellow and black strip at the bottom of it.

Have you ever seen a van or a car with something like this on it? True or false now.

Light reflected from a surface is called reflected light.

The correct answer here is true.

Can we justify our answer? Is it because reflection involves a light source and a reflective surface, or is it because reflection involves a light source and a shadow? The correct answer here is A, because reflection involves a light source and a reflective surface.

Alex and Andeep will carry out a test to compare the amount of light reflected from the surface of different materials.

Here, you can see a type of material that they're holding, and there's a torch, which is 20 centimetres from the material.

They're measuring that distance using a ruler.

And they also have a data logger 10 centimetres from the material.

Now, you might have a data logger that looks a little bit like this.

This is able to read different types of information about temperature, about light, and also sound.

There are also apps that you can download that will turn any device into this as well, and measure the temperature, measure the light, and even measure distance in some cases.

So here is what Alex and Andeep will use.

There's their data logger and there's a torch.

If you have a go at this experiment, yours might look similar to this, or you might use some slightly different materials.

It says what I need there.

A ruler, a data logger, a torch.

The materials they're gonna use are white card, black card, foil, baking paper, a plastic bag, cotton fabric, mirror, and laminated paper.

Hmm.

It's a really good idea to write down all the items that you're going to need.

That means that when you're going to go and fetch them, you're not gonna forget anything.

Here is what Alex and Andeep will do.

Here's their plan.

What I will do, it says.

Make the room as dark as possible.

Place the light source 20 centimetres away from the material.

Place the data logger, facing the material, at a distance of 10 centimetres away from the material.

Record the measurement in lux shown on the data logger, and repeat with each type of material.

We're going to do this plenty of times with each of the materials just to test it.

A data logger can be used to record the amount of light reflective from different surfaces.

You remember I said before that sometimes, you might be able to download an app that can help your device do this.

Andeep says, "We'll record the amount of light reflected in lux, which is also written as lx." A little bit like distance, it is sometimes measured using centimetres, and then you write that as cm.

Have you ever measured light before, or have you ever taken a reading or seen a reading like this in lux? Let's stop and think.

What do scientists use to record data about light? Is it a data logger, a clock, or a tape measure? The correct answer here is a data logger.

True or false? Scientists measure light in centimetres.

The correct answer here is false.

Hmm.

Can we justify our answer here? Is it because they measure it in lux, or do they measure it in minutes? The correct answer here is A, scientists measure light in lux.

Alex and Andeep will record the data that they collect in the table.

A little bit like this one here.

You can see one column is about the material and the other column is about the amount of light reflected.

They're going to need to be careful to put all of their answers into the correct columns.

They need to write down the material and then measure each part of the light and write it down straight away so they don't forget.

The table has headings and the correct unit of measurement, just like we went through before.

There are the headings there: one for material and one for the amount of light reflected.

This is the unit of measurement.

So why do you think that this is important? Why have we focused so much on these headings? Have a discussion and restart the video when you've done that.

So why is it so important? Alex says it's important to use headings for each column and the correct unit of measurement so that other people can understand the data we collect.

You know, if there were no headings, then no one would have a clue about what all this information was that was written down.

Stop and think.

We can record the results of an investigation in a plan, prediction, or table.

The correct answer here is in a table.

Who do you agree with here? Do you agree with Aisha? She says, "We can use our results to make decisions about different materials." Laura says, "We can use our results to make decisions about different light sources." Jun says, "We can use our results to make decisions about different data loggers." Hmm, who's got it right? The person that I would agree with is Aisha.

We can use our results to make decisions about different materials.

Here is Task A.

You need to carry your own test, or you can use Alex and Andeep's plan to answer this question.

How much light is reflected from the surface of the different materials? Andeep says you can record your results in a table like this, or maybe you can come up with your own.

So, have a go setting up this investigation.

Record your results carefully in the table as you go.

Best of luck.

Restart the video when you've done that.

How did you get on? Now, your results might be similar to this depending on the materials that you tested.

So the white card, that had 95 lux; the black card was 15 lux; the mirror was 430 lux, wow, that's a lot; and foil was 103 lux.

Here's the next list of results as well.

There's baking paper that was 35 lux; the plastic bag, 32 lux; cotton fabric at 66 lux; and laminated paper at 79 lux.

Wow, a varied amount of results there.

I wonder what this tells us.

What can we gather from this data? Does it matter the type of fabric or item that we're shining our light onto? Hmm.

The next part of this lesson is called evaluating an investigation.

So Alex and Andeep carried out their investigation to compare different materials based on how reflective they are, and here are their results.

And the amount of light reflected is measured in lux in the right-hand column there.

Andeep says, "We are going to use our results to help us to make decisions about different materials." Alex says, "Oh, then I can compare the reflective properties of different materials and choose a suitable material for a reflective strip on my hat." That's a good idea.

Then, in the winter, when it's usually a lot darker, you can be warm and you can be seen.

So let's use Andeep and Alex's results to compare the amount of light reflected from the surface of different materials.

Which materials reflected the most light? Have a look at all the results there and discuss.

Restart when you've done that.

Well, what did you decide? Let's find out more.

Andeep's here to help, and he says, "The materials that reflect the most light are the mirror and the foil." Alex says, "Well, I think this makes them the most suitable materials for my hat because I'll be able to see them more clearly when light shines onto them." What do you think? Has Alex got it right? Pause and think.

Restart when you've done that.

So, what do you think? Has Alex got the right idea here? Well, yes, I think he has.

If he chooses one of these items, he's going to be seen really easily, isn't he? So what else can our table tell us? Andeep says, "Are there any materials that didn't reflect any light?" Hmm.

What do you think? Have a look at the table there and discuss.

Restart when you've done that.

Were there any items that didn't reflect any light? Well, all materials reflected some light.

All of them have got some reading, haven't they? Alex says, "Well, I wonder which materials are least suitable reflecting light.

The black card reflected the least amount of light, so that's not as suitable." Which other materials reflected very little light? Have a look at the table and discuss.

Restart when you've done that.

Which materials did you choose? Well, let's have a look through the rest of them and summarise some of our findings.

Andeep says, "The mirror and the foil reflected the most light.

They both have smooth, shiny surfaces." Do you agree with Andeep and Alex here? Pause the video and discuss.

Restart when you've done that.

Alex says, "Yes, materials that have a smooth surface, like the mirror and the foil, are best for reflecting light." So I wonder which items weren't that useful? So I wonder which items didn't reflect much light? Are they gonna have any use for anything else? Hmm.

I wonder what you think.

Stop and think.

True or false? Materials with smooth surface reflect the most light.

The correct answer here is true.

Can we justify our answer? Is it because materials with dark and dull surfaces, like black colour, don't reflect light? Or is it because materials with smooth and shiny surfaces, like foil and mirrors, reflect the most light? The correct answer here is B.

Materials with smooth and shiny surfaces, like foil and mirrors, reflect the most light.

Andeep says, "Well, now that we've completed our investigation, we need to evaluate it." Hmm.

Evaluate it, and I suppose that means, then, that they can improve it.

What does improvements mean? Pause the video and discuss.

Restart when you've done that.

So how are they going to improve anything? Well, Alex says, "Well, when we evaluate something, we think about what we did and suggest changes or improvements." Of course.

What did you discuss about them improving things? Could they have improved anything else? Scientists evaluate every stage of an investigation to suggest improvements.

Alex and Andeep evaluate their investigation then.

It says, "Well, I'd improve our investigation by testing more materials.

This would help us to check if all smooth, shiny materials are good at reflecting light." Well, that's quite a big task, isn't it, if they were going to go and test every material that they could find like that? Andeep says, "Well, I'd improve our investigation by testing the materials in a darker room, then we would know that the data log is recording levels of reflected light instead of any other light in the room or from outside coming in through the window." Of course, yes.

If there's other light coming through, that's going to distract things, isn't it? Do you have any other improvements to suggest? Maybe you've got some ideas from your own experimenting.

Pause the video and have a discussion.

Who do you agree with most here? Do you agree with Izzy? "Evaluating an investigation means that we do the investigation again." Jacob says, "Evaluating an investigation means we change everything that we have done." And Sofia says, "Evaluating an investigation means we think of ways to improve what we have done." Who's got it right? I agree mostly with Sofia, who says, "Evaluating an investigation means we think of ways to improve what we have done." Here's Task B.

Look at the results from your own investigation and compare how much light is reflected from the surface of different materials.

Step one, what kind of materials are most suitable for reflecting light, and why? Step two, what kind of materials are least suitable for reflecting light, and why? Step three, what should Alex make a reflective strip for his hat from? Have a go answering these questions.

You can also use this slide here, which shows you some sample results from Alex and Andeep's investigation.

Best of luck.

Restart the video when you've done that.

How did you get on? Well, your answers could be similar to this.

The first part here, Andeep says, "Well, the mirror and the foil reflect the most light.

These are both smooth, shiny materials, so I think that smooth, shiny materials are the best at reflecting light." This is step two.

Alex says, "The black card reflected the least amount of light.

I think this is because it is a dark and dull material." Excellent thinking.

Yes, if it's a dull material, it's surely not going to reflect much.

And the third part, "The mirror reflected the most light because it was smooth and shiny.

To make the strip for my hat, I need a material that is smooth and shiny like a mirror, as it will best reflect light from my torch." Excellent, then Alex is going to be seen, and he is gonna be nice and warm in the winter, isn't he? I wonder what other things you found out from the findings that you have from these different investigations? Here's the final part of this task.

Part four, evaluate your own investigation, or you can use Alex and Andeep's.

How can you improve it? Pause the video and discuss.

Restart the video when you've done that.

Well, your ideas could have been similar to these.

Andeep says, "I can make more accurate measurements by fixing the torch in position 20 centimetres away from the material, rather than holding it in place and moving it around." Alex says, "I can improve my investigation by testing materials, such as black fabric and wood, to check how much light is reflected by other materials." Excellent.

Having a good look and evaluating your own investigation is a good way to improving yourself in the future.

You can then remember what it is that you've done and improve things, so you get a better outcome next time.

Let's summarise our lesson.

When light travels towards a surface and bounces off it, this is called reflected light.

A data logger could be used to record the amount of light in lux.

The results of an investigation can be recorded and used to make decisions.

The best surfaces for reflecting light are very smooth, such as a glass mirror.

Scientists evaluate investigations to suggest improvements.

Well, hopefully, you've got some good ideas about how best you can be seen, make sure that you are safe, and use some reflective clothing or other items when you're outside in the dark.

I'm Mr. Wilshire, thank you very much for listening.