Hello, my name is Mrs. Maharin, and I am so excited to be learning with you today.

Today we are going to be learning all about measuring reflected light, and we are going to be doing an investigation.

Welcome to today's lesson from the unit light and how it travels.

Your learning outcome today is I can investigate how changing the angle of a mirror affects the angle of reflected light.

And we are going to be touching on some of your previous learning all about how to measure angles.

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

Now, here are your key words for today.

You don't need to write these down because I am going to be referring to these throughout today's lesson.

But if it makes it easier for you, and you would like to write them down, you can do so now.

Fabulous, well done.

And here are all of the definitions for those keywords.

Again, I am going to be referring to these definitions throughout today's lesson, but if you would like to, you can pause the video here and write them down if it helps you.

Fabulous, well done.

And now your lesson today is broken into two parts.

Let's begin with the first part today, which is investigating reflected light.

Now, Izzy has been learning about reflected light.

She knows that if you change the angle, that light hits the surface, then the angle of reflection will also change.

So we learned a little bit about this in the previous lesson.

Now to find out more about this, Izzy planned an investigation to answer the enquiry question, how does the angle of light hitting a surface affect the angle of reflected light? So if you remember, we also planned an investigation into this question here.

Now, in Izzy's plan, she decided that she was going to shine a torch towards a mirror.

Now, why do you think Izzy chose a mirror rather than a wall in her plan? Why is a mirror a better option here? I'll give you five seconds to think about your answer.

If you need longer, you can pause the video here, and you can come back once you are ready.

Off you go.

Fabulous, well done.

So mirrors are highly reflective.

So it's the perfect surface for Izzy to have chosen.

And they are sometimes used to deliberately change the direction that light travels in.

Now let's have a look at this picture here.

So we can see that we have the mirror just to the side over there.

We have a torch and the light is coming in, so you can see it in this diagram here, and then it's reflecting off, and we can see the angle there that it's created.

Now, Izzy's teacher gave her a piece of paper with a mirror line, and the normal line drawn at a right angle to this.

And Izzy placed her mirror on the mirror line and shone a torch towards the mirror in a dark room.

And she marked the position of the incoming and reflected light on the paper, and then she numbered this.

And Izzy repeated the test, shining the torch from different angles.

Now, Izzy turned the room light on and moved the torch and the mirror away from the paper.

And then she began to join up the marks for each number to show the different angles of light.

So we can see how she's done that here.

Now Izzy connected all the same numbered incoming and reflected beams. So if you need to, you can pause the video here, and you can have a really good look at this just to make sure that you understand.

Fabulous.

Then what she did is she took a protractor to measure the angles between the lines she had drawn and then the normal line.

So remember, the normal line sits at a 90-degree angle.

So let's have a look at this question.

It says, what happens when you change the angle that light hits a surface? Does it a, the angle of the reflection stays the same, b, the angle of reflection changes, or c, the angle of reflection disappears? So I'll give you five seconds 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, the angle of reflection changes.

Now let's do a quick true or false.

If you want to investigate how light is reflected, a mirror would be a good surface to use.

Is that true or is that false? Again, 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.

Fabulous, well done.

So the answer is true.

Now let's see if you can justify your answer as well.

So is it a, mirrors are highly reflective and light can only reflect off shiny surfaces, or b, mirrors are highly reflective so they can be used to change the direction of beams of light? So again, I'll give you five seconds to think about your answer.

If you need longer, just pause the video here.

Okay, off you go.

Fabulous, well done.

The answer is b, mirrors are highly reflective so they can be used to change the direction of beams of light.

Now here is your first task.

And it says carry out Izzy's investigation or one that you have planned yourself.

So it could be the one that you planned in the previous lesson if you did do that one.

And then collect data to answer the enquiry question.

So how does the angle of light hitting a surface affect the angle of reflected light? So you think going to think really carefully about that.

So do the investigation, and then think really carefully about this enquiry question.

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

Off you go.

Okay, so let's have a look at how Izzy did it.

Now you may have done it like this.

So you may have done a wide angle of reflection like this one, and then you may have had a narrow angle of reflection.

So she's done two by having a look to see how the angle of light hitting a surface affects the angle of the reflected light as well.

Now let's have a look at Izzy results.

So it says here, along the top, it says angle between incoming light and the normal line.

So she's got 15 degrees, 20 degrees, 70 degrees, and 80 degrees.

And then the angle between the reflected light and the normal line, she's got 17, 20, 70, and 81.

So very, very close to the first column there.

Okay, now it is time for us to do the second part of our learning today, which is the angle of reflected light.

Well done, you are doing really, really well.

So Izzy is looking at the results of her investigation with her friend Jacob.

So they're trying to work out if there is a pattern here in her data.

Now, before we move on, can you identify a pattern here between the angle between the incoming light and the normal line and the angle between the reflected light and the normal line? So I'll give You five seconds to think about your answer.

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

Okay, off you go.

Fabulous, well done.

So Izzy and Jacob identify a pattern.

They notice that each time, the angle of incoming light is the same or almost the same as the angle of reflected light.

Izzy's sister explains what she knows about this.

And Izzy's sister says, "Reflected light bounces off a surface at the same angle as it hits it." So here is a diagram showing light being reflected off a surface.

If the angle between the incoming light and the normal line is 40 degrees, then the angle between the reflected light and the normal line should also be 40 degrees.

So if you've done this accurately, then both of those angles should be exactly the same.

Now, light which hits surfaces with a wide angle to the normal line will also be reflected at a wide angle as well exactly like this diagram is showing us here.

And again, light which hits the surface with a narrow angle to the normal line is also going to be reflected at a narrow angle.

Now let's do a quick check of your learning.

And it says, which letter would the reflected light hit? Would it hit a, b, or c? So have a really good think here.

Where would your normal line be, and how do you know which letter it's going to hit? Think about everything that we've just been learning together.

Okay, I'll give you five seconds to think about your answer, but if you need longer, just pause the video here.

Okay, off you go.

Fabulous, well done.

So it would be b.

Now, if light hits a mirror at 30 degrees, what angle would the will the reflected light be? So if light hits a mirror at 30 degrees, what angle will the reflected light be? Will the angle of the reflected light be 130 degrees, 90 degrees, or 30 degrees? So again, think about what we've just learnt about the angles and what they should be and have a go at answering this question.

So I'll give you five seconds.

If you need longer, you can pause the video, and you can come back once you have an answer.

Okay, off you go.

Fabulous, well done.

The answer is 30 because it should be the same size angle.

Now Izzy looks back at her results to consider her evidence.

Now, two of Izzy's pair of angles are very similar, but they're not exactly identical.

And Izzy is really worried that her results are wrong.

So can you help Izzy, what do you think may have gone wrong here? Does it mean that all of her results are wrong? What can we say to Izzy to help her out here? So again, I'm going to 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 come back once you've got an answer.

Okay, off you go.

Fabulous, well done.

So Jacob is on hand to reassure Izzy.

And he says, "Measuring angles is difficult.

And also, sometimes light beams are slightly unclear, making it really hard to know exactly where to put the cross.

Sometimes measurements may not be perfect, but you shouldn't worry if you are very, very close," because Izzy was only one degree off for both of those.

So really, her measurements were accurate.

And it's okay if you have some small errors or differences in a task like this.

So Izzy's results are close enough to act as evidence to support the fact that reflected light bounce off a surface at the same angle as it hits it, which we've been able to see by carrying out Izzy's investigation or the investigation that you planned if you did the previous lesson.

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

It says true or false? When you measure angles, it's acceptable for results to vary slightly.

Is that true or is that false? I'll give you five seconds to think about your answer.

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

Okay, off you go.

Fabulous, well done.

The answer is true.

And let's see if you can justify your answer as well.

So is it because a, it's difficult to measure perfectly, so up to two degrees either side of the real measurement is acceptable, or the degrees are not all the same size on different protractors, so results will vary? So again, I'll give you five seconds to think about your answer.

If you need longer, just pause the video here.

Off you go.

Fantastic, well done.

The answer is that it is difficult to measure perfectly.

So up to two degrees either side of the real measurement is absolutely fine.

Okay, so what you're going to do now is you are going to review your data from task A.

Does it provide evidence to support the statement that reflected light bounces off a surface at the same angle as it hits it? And again, remember that you can allow measurements which are two degrees different to each other to count them as matching each other.

So please don't worry if they're not exactly, exactly the same.

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

Off you go.

Fabulous, well done.

So here are another set of results.

So we can see here on the left-hand side, we have 25, 40, 55, and 75.

And on the right-hand side, they are off.

Three of them are off by one degree, okay? So again, there may be some differences between pairs of angles, but these are all equal to or less than two degrees.

So it really doesn't matter.

And these results would be considered as being accurate and providing evidence that reflected light bounces off a surface at the same angle as it hits it.

So please don't be concerned if some of yours have come out two degrees less or two degrees more.

Now here is another set of results.

Now we can see on the left-hand side, we've got numbers like 25 degrees, 40 degrees, 55 degrees, and 75 degrees.

Now on the right-hand side, however, it's numbers like 16 degrees, 41 degrees, 61 degrees, and 69 degrees.

So the only one that would be accurate there is the second one where it's only one degree off.

The others are much more than just two degrees.

So these results are not going to provide evidence that reflected light bounces off a surface at the same angle as it hits it.

So here is a summary of your learning today.

It says if you change the angle that light hits a surface, the angle of reflection will also change.

Mirrors are highly reflective.

They are sometimes used to deliberately change the direction that light travels.

Reflected light bounces off the surface at the same angle as it hits it.

And when you measure angles, it's acceptable for results to vary slightly because it is difficult to measure perfectly.

Now, I am so proud of your learning today.

You've worked really hard, and you've tried to be so accurate with the results that you have achieved.

So well done, well done for using your critical thinking and working so hard.