Hello, my name is Mrs. Mehrin and I'm so excited to be learning with you all today.

Today we are going to learn all about how light travels.

Welcome to today's lesson from the unit Light and How it Travels.

Your learning outcome for today is: I can explain that light travels in straight lines.

Now, I know that learning can sometimes be a little bit challenging, but that's okay because it just means that we're going to work really hard together and we are going to learn lots of fabulous new things.

Now, here are your key keywords for today's lesson.

I am going to go through all of these keywords with you throughout the lesson, so you don't need to write them down, but if you would like to, you can pause the video here and jot them down.

Off you go.

Fantastic, well done.

And here are all of the definitions for today's keywords.

Again, I am going to be referring to these throughout the video, but if you would like to, you can pause the video and jot them down or you can just come back to this point in the video at any point.

Fantastic, well done.

So our learning today is split into two sections.

We have travelling light as our first one.

Let's begin.

Have you ever been to a place where there is no light? What was it like and what were you able to see? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic, well done.

So we need light to be able to see things, and when there is no light, you can't see anything at all.

So sometimes you may be in your bedroom with the lights turned off and the curtains closed and you may start to make out some objects in your room.

That just means that there must be some light coming through from somewhere.

So that might be through the crack in the door or under your door.

It might even be, for example, the streetlights or the moonlight seeping through your curtains.

But there has to be at least some light in order for you to be able to see something.

However, if you are somewhere where there is absolutely no light whatsoever, that is when you cannot see or make out any objects at all.

So I want you to really think now, where does light come from? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic, well done.

Now let's discover where light comes from.

Before we do that, we are just going to do a quick check-in to make sure that you've understood what we've learned so far.

So if you were in a room with no light, what would you be able to see? So remember, if there is absolutely no light at all, what are you going to be able to see? Are you going to be able to see most things but only after your eyes have got used to the dark, only shiny things, or nothing? I'll give you five seconds to think about your answer.

But if you need longer, that's absolutely fine.

Just pause the video and come back when you are ready.

Off you go.

Fantastic, well done.

The answer would be C, nothing.

If there was no light at all, you would be able to see nothing at all.

Now, light can come from different places like the sun or from fire or from electrical devices such as lamps or torches.

Now, things that produce light are called light sources.

Now, Sam says, "I wonder how light travels from a light source.

Do you know?" And Lucas replies, "I think light does not travel.

It stays at the light source and makes things look bright." So remember, a light source is something that produces light.

So what do you think of Lucas's explanation? Have a little think.

Off you go.

Fantastic, well done.

So light travels outwards from a light source in all directions.

For example, light from the sun.

When you turn on a lamp, light continuously travels out of that lamp in all directions that we can see.

So here you have light from the sun and you have light from a light bulb.

Now Sam and Lucas are thinking more about how light travels.

And Sam says, "I think light travels in wavy lines, or waves, a bit like how sound travels." And Lucas says, "I think light travels in zigzag lines like lightning bolts." What do you think? I'd like you to think about this answer carefully.

I'll give you five seconds.

However, if you need longer, you can just pause the video here, come back when you are ready.

Off you go.

Fantastic, well done.

So let's do a quick check-in of your learning.

It says, which statement about light is true? Is it A, light does not travel; B, light travels out from a light source only in one direction; C, light travels out from a light source in all directions; or D, light travels into a light source? So I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here and come back when you are ready.

Off you go.

Fantastic, well done.

The answer is C, light travels out from a light source in all directions.

Now here is your first task.

It says, set up some thick card, as shown in the diagram, so that the holes are lined up correctly.

So here we have a torch.

We have some pieces of card.

We have three pieces of card with holes in the middle.

And then a final card that has no hole cut out.

So you're going to dim the lights and switch on a torch opposite the hole in the first piece of card.

And it says, what do you observe on the final piece of card? So in order to ensure that all of the holes are lined up correctly, just have a look through the holes and make sure that you can see all three holes so that they're all in a straight line.

So I'll give you some time now to have a go at that activity.

I'd like you to pause the video here so that you can do that.

Off you go.

Fantastic, well done.

So depending on what you observed, what does this tell you about travelling light? Think about the statements that Sam made and Lucas made.

What does it tell you about how light travels? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic, well done.

So now it says to rearrange the cards so that the holes are not lined up.

So a bit like this.

Dim the lights again and switch on the torch opposite the hole in the first piece of card.

Now what do you observe on the final piece of card? And depending on what you observe, what does it tell you about travelling light, about how light travels? I'll give you some time now.

I'd like you to pause the video and have a go at this task and think about the answers to those two questions at the end.

Off you go.

Fantastic, well done.

So what did you observe about travelling light and why? So it says when the holes in the cards are all lined up, the light from the torch can be seen on the final piece of card.

And this is because light travels in straight lines through all three holes.

Now when the holes in the cards are placed in an uneven line, the light cannot be seen on the final piece of card.

And this is because light travels only in straight lines and it cannot bend.

So now that takes us on to our second part of our lesson, which is recording how light travels.

We see light at the light source and where it reaches the object.

However, the beam of light travelling between them is not visible.

So here we are using a torch for a light.

So we see light at the light source and we see light at the object.

Light travels in straight lines through the air, in the space between the light source and the object, even though we can't see it.

Now Sam wants to explain to her friends how light travels in straight lines.

Sam says, "It's difficult to record how light travels as you can't see it travelling in between the light source and the object, even though it is there." What are some different ways that Sam could record what she has learned about how light travels? Now I'll give you some time to think about this answer.

I'd like you to pause the video here and have a go at answering that question and then we'll come back and discuss it.

Off you go.

Fantastic, well done.

So Sam has decided to make a model.

She rolls out wool and she pulls it tight.

So here we have a straight line of wool.

On the end, she has a torch, the wool represents the light, and then she has the pencil, the object at the end.

And she says, "My model shows how light travels continuously from the light source to the object in straight lines." What do you think of Sam's model? I'll give you five seconds to think about your answer, but if you need longer, that's absolutely fine.

Just pause the video here.

Off you go.

Fantastic, well done.

Now let's do a quick check-in of learning before we look back at Sam's model.

And it says, how does light travel? Is it A, in scattered rays; B, in wavy lines; or C, in straight lines? I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic, well done.

The answer is in straight lines.

So Sam says, "I don't think my model is a very scientific way of presenting how light travels.

What do real scientists do?" Scientists use a type of a drawing called a diagram to record scientific information, such as how light travels in straight lines.

Now Sam's neighbour is a scientist and Sam asks her how scientists use diagrams to record how light travels.

And she says, "Travelling light must be drawn as straight lines with a ruler.

Every line must have an arrowhead pointing in the direction that the light is travelling." Sam has one more question to ask about using scientific diagrams to show how light travels.

Sam says, "I learned that light travels from a light source in all directions.

So should I draw lots of arrows on my diagram, not just one?" And Sam's neighbour, the scientist said, "Light does travel from a light source in all directions.

However, scientists choose to represent this in a diagram with just one line of travel." So here is how to draw a scientific diagram to show how light travels from a lamp to a mug.

So step number one, you draw a simple diagram of a lamp.

Step two, you draw a simple diagram of a mug.

So again, these are just simple diagrams, it doesn't need to be anything fancy.

Then you're going to join the lamp to the mug using a straight line drawn with a ruler.

Now it's really important that you use a ruler, because if you don't, then your line becomes a little bit wavy and that's no longer scientifically accurate.

So it must be a straight line drawn using a ruler.

Then step four is to add an arrow to the line to show the direction that the light is travelling in.

So remember, the light travels from the light source, which here is the lump.

So if you were to draw the arrow facing the opposite way, you would be saying the mug is the light source.

So you need to be really careful here.

So let's do a quick check-in of your learning.

Which of these correctly shows how light travels using a scientific diagram? Is it A, B, or C? So I want you to just pause the video here, have a really good look at these three diagrams and come back once you have an answer.

Off you go.

Fantastic, well done.

The answer would be A, because B has wavy lines, and C, although it is a straight line, you can see the arrows pointing in the wrong way.

So it's almost saying that the beaker is the light source.

So C cannot be right, it's got to be A.

Well done.

So let's have a look at task B.

It says, look at these pictures of light sources.

Draw two scientific diagrams to show how light travels from the torch to a box and from a candle to a box.

So I'd like you to pause the video here.

Remember, in your scientific diagram, the actual pictures of the objects do not need to be complicated.

They can just be simple drawings.

So it can be a simple drawing of a torch, a simple drawing of a candle, and a simple drawing of a box.

So I'd like you to pause the video here and have a go at that activity.

Off you go.

Fantastic, well done.

So here is your diagram to show light travelling from a torch to a box.

So we can see we have the picture of the torch, nice and simple.

We have a simple picture of a box.

We have a line, a straight line using a ruler, and then the arrow is pointing in the correct direction because it's saying that the light is coming from the torch and hitting the object, which is the box there, rather than the other way round.

And here we have the diagram to show light travelling from the candle flame to the box.

So again, a nice, simple diagram of a candle, a nice, simple diagram of a box, a straight line using a ruler, and the arrow is also pointing in the right direction, it's going from the candle to the box.

So have a look at your diagrams. Are they similar? Are they different? Is there anything that you need to change on yours? I'll give you five seconds to just have a look at yours and compare it to these.

Or if you do need to make changes, just pause the video here and have a go.

Off you go.

Fantastic, well done.

So now onto our summary of today's learning.

We need light to be able to see things.

Light travels out from a source of light in all directions.

Light travels in straight lines, and scientists use diagrams to show light travelling in straight lines.

Fantastic learning today.

You've done loads of new learning, but you've persevered and you've used your critical thinking as well.

I'm really proud of all of your hard work today.

Well done.