Hello, my name is Mrs. Mechrid, and I'm so excited to be learning all about measuring reflected light.

And today, we are going to be creating a plan.

Hello, and welcome to today's lesson from the unit Light and how it travels.

Your lesson outcome for today is, I can plan an investigation to see how changing the angle of a mirror affects the angle of reflected light.

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

Now here are your key words for today.

You don't need to jot them down because I am going to be referring to them throughout today's video.

However, if you do feel that it helps you to write them down you can pause the video here and have a go.

Off you go.

Fantastic.

And here are all of the definitions for those keywords.

Again, I'm going to be referring to these throughout today's video, but if it helps you to write them down you can pause the video here and do that.

Fabulous.

Well done.

Now your lesson today is split into two parts.

Let's begin with the first part, measuring and comparing angles.

Now, Sam has been investigating what happens when light is reflected off different surfaces.

Now when she was doing her investigation, Sam noticed that there were some patterns in her results.

So Sam says, "I observed that when I changed the angle that light hits a surface, the angle of the reflection also changed." So that's the pattern that she's noticed when she was doing this investigation.

Now scientists are always interested in finding patterns.

And scientists are interested in patterns in the angles of the incoming light and the reflected light.

Now do you know what angles are, and do you know how to measure them? I'll give you five seconds to think about your answer.

Off you go.

Fabulous.

Well done.

Now an angle is the space between two straight lines which join at a vertex or a point, just like in this diagram here.

And we can see there the vertex or the point is on the very end.

And you have a pair of lines there that meet at that point in order to form an angle.

Now as scientists, we need to be able to measure angles, and this is going to allow us to compare the angles of incoming light and reflected light and identify patterns.

So angles are not just used in maths, we can use them in science as well.

Now we measure angles using something called a protractor, like this picture here.

And it's a really useful tool which you might have used in your maths lessons.

And protractors have this line here, which is called the baseline, that's been highlighted for you in yellow.

And then you have all of these markings all the way around the outside of your protractor.

And then you have a centre hole or it might be across on your protractor.

And protractors tell us how big or how small an angle is.

And angles are measured in units called degrees.

And the symbol for degrees is this little circle here.

So 43 degrees would be written as 43 and then a little circle in the top corner there.

Now in order to measure the angle between two lines that are drawn on a piece of paper, you need to place the protractor on the paper first with the baseline lined up with one of the lines on your angle.

So remember, the baseline was highlighted in yellow on the previous slide.

So just like this.

Now this is your starting line right there.

Now you're going to slide the protractor along until the vertex, so that point in the corner, is directly over the centre cross or the hole.

So you can see, the vertex is directly on that centre cross or the hole, if it's on your protractor.

There we go.

Can you see how that lines up perfectly? So we need to make sure that it is perfectly lined up.

Then what you're gonna do is you're going to look at the degree scales.

So if you've got a semi-circular protractor like this one here.

There's usually two scales.

You have one on the inside and you have one on the outside.

Now they both start at zero degrees at one end and go up to 180 on the other.

Now if you look, they don't both start at zero on the same side.

You've got one that starts on the left-hand side and one that starts on the right-hand side.

And here you've got the outer scale.

So the outer scale, which is in black, the zero starts on the left-hand side, and that's really important to remember.

And the inner scale, the zero starts on the right-hand side.

Now use the scale which has the zero on your starting line.

So here, if we have a really good look at this angle here, you can see that the bottom line, the starting line, is pointing towards the zero that's on the left-hand side.

So the numbers that are going on the outer side, the outer scale.

So here we got the starting line is lined up with the black zero.

There you can see it really clearly.

Now you're going to find where the other arm of your angle crosses the scale that you are using, and the number at this point is the size of the angle.

So here we can see that the other arm is crossing the scale at 30 degrees.

So our angle here is a 30-degree angle.

So let's do a quick check-in of your learning 'cause we've done lots of learning so far already.

Which of these pieces of equipment is used to measure angles? Is it A, a compass, B, a protractor, C, a force metre, or D, an angler? So I'll give you five seconds now to think about your answer.

If you need longer, you can pause the video here.

Off you go.

Fabulous.

Well done.

The answer is B, a protractor.

Now let's have a really good look at this question, and it says, what size is this angle? Is it A, 20 degrees, B, 160 degrees, C, 15 degrees, or D, 40 degrees? So what is the size of the angle here? I'll give you five seconds to think about your answer.

Off you go.

Fabulous.

Well done.

The answer is A, 20.

Now Sam has spotted angles all around her room.

It says measure the angles created by the items in Sam's photo.

So if we have a look at the first picture, we have the ruler and it looks like a blue book, and you're measuring the angle between the two of them.

Then we have two pens and you're measuring the angle created there, and you can see that the white lines have been drawn along the edges to help guide you.

Then we have a game and what looks like another book.

And then we have a book and a box.

So you're measuring the angles in between those items there.

So what you're going to do now is you're going to pause the video, and you're going to have a go at that activity.

Off you go.

Fabulous.

Job well done.

So let's have a look at the angles that have been measured here.

So we've got 24 degrees on the first one, 132 degrees on the second picture, 16 degrees on the third picture, and 64 degrees on the last picture.

Now what's really important is that your measurements match these ones below.

However, if you are off by say one degree, so say for example, the first one you got 23 degrees or you got 25 degrees, that would still be fine because it might not be exactly the same.

You can be off by one degree.

Now we are on to the second part of our learning today which is planning for our investigation.

So when light is reflected off a surface, the space between the straight line of the beam of light and the surface it hits is called an angle.

So here we can see a diagram of a torch and the surface.

Now we can measure angles of light using a protractor.

So Sam says, "Do I put my protractor here and measure between the beam of light and the surface?" I'll give you five seconds to think about your answer.

Off you go.

Fabulous.

Well done.

So that would be wrong.

Izzy is helping Sam.

And Izzy says, "When we measure the angle of light hitting a surface, we measure the angle between that light and something that's called the normal line." So here we have the normal line.

The normal line is an imaginary line that is at a right angle to the surface.

So here we can see that it's a right angle because there's a square there to show that it is a right angle, it's 90 degrees.

So this diagram shows the angle of a light beam hits a mirror.

So what is the angle between the light and the normal line here? I'll give you some time now to think about that.

If you'd like, you can pause the video and you can measure it.

Off you go.

Fabulous.

Well done.

So we would've put our protractor here like this.

Now our protractor would have to go on an angle here, because otherwise we aren't going to get that measurement correct.

And we can see that it lines up with 70 degrees.

So the angle's 70 degrees.

Now when we measure the angle of light hitting a surface, we measure the angle between that light and what? Is it the mirror line, the surface line, or the normal line? So I'll give you five seconds to think about your answer.

If you need longer, just pause the video here and then you can come back whenever you are ready with an answer.

Okay, off you go.

Fabulous.

Well done.

So the answer would be C, the normal line is what you are measuring, the angle between the light and the normal line.

Now it says here, which of these angles is the correct one to measure to find out the angle of incoming light? Is it A, B, or is it C? So again, I'll give you five seconds to think about your answer.

If you need longer, that's absolutely fine, you can pause the video here and you can have a go at that.

Okay, off you go.

Fabulous.

Well done.

The answer would be B.

Okay, so here is the second part of your learning today.

And it says, plan an investigation to answer the inquiry question: How does the angle of light hitting a surface affect the angle of reflected light? So how does the angle of light hitting a surface affect the angle of reflected light? So you're going to discuss this in small groups.

Now I want you to think about the following things.

What are you going to do? What are you measuring? How are you going to measure that? Which variables are you going to change and which variables are you going to keep the same, or which variables are you going to control? So think really really carefully about what you have learned so far about the angle of light which is hitting the surface and how that affects the angle of the reflected light.

And apply that to all of these questions that are listed or all of these statements that are listed below.

Now what you're going to do is you are going to record your plan with a labelled diagram and numbered instructions.

So make sure that you've got a diagram like the one that we have had a look at already.

And if you need to, you can always go back in the presentation here in the video and you can see what those diagrams look like.

That'll give you a really good understanding of exactly what you need to do.

And then when you've got your instructions, just make sure that you are numbering those as well.

Okay, so you're going to need to pause the video here and have a go at this activity.

Off you go.

So let's have a look at Izzy's.

So Izzy has got her piece of paper, she's got her protractor, and she's got the mirror.

Then she's got the torch, and the torch is hitting the surface.

And then she's got, in her diagram, the normal line as well to show exactly where that is.

So your diagram might be a little bit like Izzy's.

So what I want you to do now is just to pause the video make sure that you've got everything that you need to, and you've included everything in your plan for your investigation.

So make sure you've got the protractor labelled, you've labelled the mirror, the normal line, the torch, the piece of paper, and the protractor.

So have a go at doing that.

I'd like you to pause the video now.

Off you go.

Fabulous.

Well done.

You are doing so well.

So let's see what Izzy wrote.

She said, "We'll place a piece of paper on the desk and stand a mirror on it, using sticky tack to hold it up.

We will stand a bit of cardboard opposite the mirror using sticky tack to create a wall." So Izzy has been really specific about exactly what she's going to do in this plan, which is fantastic.

And she says, "We'll cover two sides of the torch lens with masking tape so that it only makes a narrow beam of light." Again, that is so important because you don't want a thick beam of light which is going to make it much harder to measure that angle.

And then she says, "Then we'll shut the window blinds and turn the lights off." Again, really, really helpful to have a dark room to do this in.

And then she's put, "Next, we'll rest the torch on the desk, turn it on and shine it towards the mirror." She says, "We'll use a pencil to mark where the beam starts at the torch, where it touches the mirror and where it is reflected on the cardboard.

We'll use a pencil and a ruler to join up the lines and we will draw a line to mark where the mirror was." And lastly she says, "We'll use a protractor to measure the angle between the normal line and the incoming light and then we'll do the same between the normal line and the reflected beam." And lastly, "We'll try it again with the torch at a different angle.

Each time we try it, the only variable we will change is the angle of the torch.

We will control all the other variables." So she's going to keep it all the same, the rest of it all the same.

Now what I want you to do is pause the video here.

I want you to go back in the video and have a look at Izzy's plan and then have a look at your plan.

Is it similar or is it different to Izzy's? Do you have all of the main bits that you need included in your plan? Okay, off you go.

Fabulous.

Well done.

Now we are on to the summary of your learning.

An angle is the space between two straight lines which join at a vertex or point.

A protractor is a piece of equipment used to measure and draw angles.

When we measure the angle of light hitting a surface, we measure the angle between that light and the normal line.

And the normal line is an imaginary line that is at a right angle to the surface.

Now there has been lots and lots of new learning for you to do today, but you have done brilliantly.

I am so proud of your hard work and your dedication in this lesson.

Well done.