Lesson video

Hello, everyone.

How are you today?

I hope you're feeling really good.

My name is Ms. Afzal and I'll be your teacher for this lesson.

I'm feeling very pleased about that because today we are looking at light.

We're looking at reflected light.

I wonder if that's something you've thought about before, if you've heard about it, and don't worry whether you have or you haven't.

We'll be getting right into it today.

Our lesson is called "Reflected Light: Plan," and it comes from the unit of work, Introduction to Light and Shadows.

So if you're ready with some energy, focus, and enthusiasm, we'll be begin our lesson.

The outcome for today's lesson is I can plan how to compare different materials based on how reflective they are.

I hope that sounds of interest to you.

We have some keywords in our lesson.

Let's go through them one at a time.

My turn, your turn.

Reflect.

Reflective.

Surface.

Data logger.

Lux.

Good to hear those words.

Let me go through them one more time.

We have reflect, reflective, surface, data logger, and lux.

So, what do these keywords mean?

Let's find out.

Reflect is to reflect light is when light hits a surface and bounces off.

Reflective.

A mirror is a reflective surface.

Mirrors reflect a lot of light.

Surface.

Surface is the top or outside layer of something.

Data logger.

Data loggers are electronic devices which monitor and record changes in the environment over time.

And lux.

Lux is the unit used to measure the brightness of light.

I rather like that word.

So these are our keywords.

Let's look out for them.

Let's listen out for them.

Let's think carefully about them.

They will all be coming up in our lesson today.

Today's lesson is called "Reflected Light: Plan," and it has two learning cycles.

First of all, reflected light and then measuring reflected light.

Let's begin by exploring reflected light.

Alex and his brother are on a nighttime walk with their dad.

As a car passes and shines its headlights, Alex notices parts of a traffic cone appear to light up too.

How interesting.

And then we can see Alex and his brother and a cone.

Why do you think this happens, that parts of the traffic cone appear to light up too as the car passes and shines its headlights?

Pause here and share with someone.

What are your ideas?

Thanks for sharing.

Alex's brother explains that the cone is not a light source, the material of the cone is reflecting light.

There's our keyword, reflecting.

And here we can see in this image, an apple being reflected by a mirror.

And Alex, "I've heard about reflections when I look in the mirror, but the cone is not a mirror!

" Good point.

Let's hear some more from Alex's brother, who explains that reflection involves a source of light and a surface.

When light reaches a surface which it can't pass through, it can sometimes bounce or reflect off the surface.

So we can see in our diagram there, we can see the light from the torch is heading towards the surface and then the light is reflected from the surface.

And so this is what was happening when Alex saw the light being reflected by the cone.

Parts of the traffic cone are made from a reflective material, so when light hits the surface, it bounces off.

This is called reflected light.

So we have the car headlights.

The light from those is hitting the reflective surface on the cone and then it's bouncing off of that, and that light is what Alex is seeing.

Let's have a check for understanding.

True or false?

Reflection always involves a source of light and a mirror.

Pause here while you decide.

Is this true or false?

Well done if you selected false.

And now I would like you to justify your answer by selecting one of these two statements.

Either A, reflection involves a source of light and a reflective surface, or B, reflection involves a source of light and a shadow.

Pause here while you decide.

Well done if you selected answer A.

Indeed.

Reflection involves a source of light and a reflective surface.

This is a great justification for your earlier answer.

The children stand under the nearest street light to observe if surfaces reflect light.

Have you observed any materials that reflect light?

Pause here and share with someone.

Thanks for sharing.

As the children are walking home, Alex realizes that he's lost his hat.

He and his brother can't find it in the dark even when they use their torches.

Oh no.

Such a nice red bobble hat as well.

There they are searching with torches.

Alex and his brother finally find the missing hat.

Phew.

And Alex's brother has a great suggestion here.

"You could put a piece of reflective material on your hat to reflect the light from our torches and then you'll be able to find it more easily if you lose it again.

" What a good idea.

And there we go.

Look at that reflective material.

Looks pretty good.

Here's Alex, "I found some different materials.

We could test them to find out how reflective they are.

" Here are the materials.

White card, black card, foil, baking paper, plastic bag, cotton fabric, mirror, laminated paper.

How can Alex find out which materials are most suitable for reflecting light?

Do you have any ideas?

Pause here and share with someone.

Thanks for sharing.

Here's Alex.

"I'll go into a dark room and shine my torch on different materials.

" And then we can see light from Alex's torch hitting the surface of material.

"And then observe whether they reflect any light back onto the wall.

" And now we can see light reflected by the surface onto the wall in that next line.

"These will be suitable reflective materials for my hat.

" What a great idea, Alex.

I wonder if this idea is similar to the one you came up with.

Alex begins by testing a mirror.

He holds the mirror so that it is facing the wall.

There's a mirror.

He shines a torch towards the mirror.

There's his torch.

And he looks at the wall to observe if any light has been reflected off the mirror onto the wall.

He writes down what he observes.

Pause here and share with someone.

What can you see?

What are your observations of Alex shining the torch onto the mirror, seeing if any light has been reflected onto the wall?

Pause here and share with someone your reflections on reflected light.

Thanks for sharing.

Let's have a check for understanding.

Which diagram shows how light reflects from a surface onto a wall?

Is it A or is it B?

Pause here and share with someone.

Well done if you selected B.

Indeed, we can see there the light from the torch hitting the surface and then being reflected from the surface onto the wall.

And now it's time for your first task.

I would like you to use Alex's method to test different materials to find out which materials are most suitable for reflecting light.

So here are some of our materials, white card, black card, foil, baking paper, plastic bag, cotton fabric, mirror, and laminated paper.

And what you'll do is you'll shine your light source onto the surface of your material and then you'll see whether there is any light reflected by that surface onto the wall.

And remember to dim the lights.

Pause here while you have a go at this task, testing your different materials to find out which materials are most suitable for reflecting light.

I'll see you when you're finished.

It's great to be back with you.

So how did you get on with that task of using Alex's method to test different materials to find out which materials are most suitable for reflecting light?

Here's Alex, "I observed that the mirror and the foil reflected light from the torch onto the wall, but it was difficult to tell if any other materials I tested were suitable reflective materials.

" And your results may be different depending on which materials you tested.

Well done for having a go at this task.

And now onto our next learning cycle, measuring reflected light.

Alex observed that light was reflected onto the wall using a mirror and kitchen foil.

There, we can see the light being reflected onto the wall.

"Are mirrors and kitchen foil the only reflective materials?

I thought other materials would reflect light too.

" Alex is keen to find out the answer to his question, I can tell.

And Alex's brother, "Nearly all materials reflect some light.

Mirrors, however, reflect almost all the light that hits them due to their shiny surface.

" "I would like to find out how much light is reflected from the surface of different materials.

I wonder if I can measure reflected light.

" Oh, wouldn't that be interesting?

What do you think?

Pause here and share with someone.

Thanks for sharing.

Here's Alex, "I need to find something that can measure how much light is reflected from the surface of each material.

I know that if thermometer can measure temperature and stopwatch can measure time, but what can I use to measure light?

" What do you think?

Do you know of something that can measure light?

Pause here and share with someone.

Thanks for sharing.

And here comes Andeep with the answer.

"We can use a data logger that has a light sensor to monitor and record how much light each material reflects.

" And there we can see the data logger.

Have you used a data logger before?

Pause here and share with someone if you have or if you haven't.

Thanks for sharing.

Here's Alex, "If I dim the lights in the room and shine my torch towards each material, then the data logger will display a number.

The higher the number, the more light is being reflected by the material.

Light is measured in lux.

" And there we can see a data logger and some light data being recorded.

Let's have a check for understanding.

Which of these do we use to measure and record light?

Is it A, the clock, B, a data logger, or C, a tape measure?

Pause here and share with someone.

Which of these do we use to measure and record light?

Well done if you selected B.

Indeed, it's a data logger that we use to measure and record light.

Andeep and Alex use a ruler to keep the position of the data logger and torch the same distance from the material each time.

So there we have our material on the left and the data logger, which is 10 centimeters away from the material.

So really important to keep that constant each time.

And the torch is 20 centimeters from the material, and we can see our ruler to help us with the measurements.

Let's have a check for understanding.

Who do you agree with?

Aisha, "Light can be measured with weighing scales and is measured in kilograms.

" Lucas, "Light can be measured with a measuring jug and is measured in milliliters.

" And Sam, "Light can be measured with a data logger and is measured in lux.

" Pause here and decide who you agree with.

Well done if you selected Sam.

Indeed, light can be measured with the data logger and it's measured in lux.

And now it's time for your next task.

I would like you to plan your own test to find out how much light is reflected from the surface of different materials.

Write down what you'll need and what you will do.

Remember to think about what you will change and what you will keep the same.

You could use Alex and Andeep's idea, or you might prefer to plan your own investigation.

So pause here while, first of all, you write down what you'll need for your task.

Pause here while you do this.

It's good to be back with you.

Perhaps you came up with a list like this.

What I need.

Ruler, data logger, torch, and then materials.

White card, black card, foil, baking paper, plastic bag, cotton fabric, mirror, laminated paper.

And next, pause here while you write down what you will do.

What are the different steps that you'll carry out?

Pause here while you do this.

Perhaps you came up with something like this.

What I will do.

Make the room as dark as possible.

Place the light source 20 centimeters away from the material.

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

Record the measurement in lux recorded on the data logger.

Repeat with each type of material.

I'm glad that you've been here and taking part in this really interesting test.

Well done for planning your test.

In our lesson, "Reflected Light: Plan," we've covered the following.

Reflection involves a source of light and a surface.

Light reflected from a surface is called reflected light.

Data loggers are electronic devices which monitor and record changes in the environment over time.

Light is measured in lux and can be recorded using a data logger.

And then we can see Alex very proudly wearing his hat with some reflected material on it so that he'll be able to find it next time he loses it at night.

Well done, everyone, for joining in with this lesson.

It was great to explore reflected light with you.

What is reflection?

What is reflected light?

We found out about data loggers.

We found out about measuring in lux.

I think that's a really wonderful unit of measurement.

And we've come up with a fantastic plan.

I hope you've enjoyed this lesson.

I've really enjoyed teaching you and I'm looking forward to seeing you at another lesson soon.

Until then, stay curious.