Hello scientists.

In this lesson, we're going to be looking at light and seeing.

My name is Mr. Wilshire.

Let's crack on with our lesson.

The outcome for this lesson is I can explain that light is necessary for us to see things.

There are some key words to consider as we work our way through the lesson.

The first here is eye, then it's see, after that, light, and, finally, dark.

Don't worry if you're not too sure what some of these words mean, as the definitions are up on the screen for you now.

You can have a read, and remind yourself, as you may have heard some of these words before, but don't worry if you are not too confident in all of them.

As we work through our lesson, the meaning should become more clear for you.

Pause the video now if you need to, and remind yourself on what these words mean.

The first part of this lesson is called light and seeing.

Sam and Izzy are looking at some rocks, and sorting them out into groups.

Here you can see a selection of the rocks that they have.

I wonder which part of our body we use when we look at something.

Have a little think, and discuss which part of the body do we use.

I wonder what part of the body that we use.

Well, humans use their eyes to see things.

We call this our sense of sight.

We can see things that are very near to us, and things that are really far away.

Here you can see two images, an image of some people looking at things that are very nearby, and an image of a city that's very far away in the distance.

Stop and think.

Which body parts do humans use for seeing? Is it their tongue, their skin, or their eyes? The correct answer here is their eyes.

Of course, they need to use their eyes to see things.

Some children are on a school trip and going into a cave.

They're wearing head torches and carrying hand torches.

They're looking around the cave at the different types of rock.

You can see people exploring a cave.

It can be very dark inside a cave, as there's no natural light.

No wonder they need to have torches.

The children arrive at the middle of the cave, and the trip leader asks them what they think will happen if they turn off their torches.

Hmm, I wonder.

Lucas says, "I don't think we'd be able to see anything." Alex says, "I think we'll be able to see the rocks, but it will be much harder to see them." And Sofia says, "Well, I think our eyes will get used to no light, and we'll be able to see the same as with the torches." Hmm, I wonder what you think here.

Are the children going to be able to see the same without the torches, or are they going to get used to having no light at all? What do you think? Pause the video here and discuss.

What did you think? Let's find out more.

When the children turn off their torches, I can't see anything.

Here is a cave with no light.

It's completely blank.

They stand still and wait a little longer.

Here again, is an image of a cave with no light.

"I still can't see anything at all." Why do you think the children can't see anything? Hmm, have a discussion.

So why can't the children see anything still? Hmm.

We need light to be able to see.

Our eyes can't see things if there's no light at all.

Here you can see an image of someone looking when there's plenty of light, and looking when there's no light.

The difference is quite obvious, isn't it? You can't see anything when there's no light at all.

Have you tried to look at objects when there is no light? Can be very difficult to create an environment when there's no light at all.

Closing the curtains is only gonna cut out some of the light, isn't it? I wonder if you've ever tried to look at objects when it is truly pitch black.

Discuss.

Have you ever been caught in the dark like that? Laura says, "Oh, I can see in my bedroom when there's no light at night," and Jacob says, "Well, that's because there is some light coming from your clock." Here's an example of Laura's clock.

Jun says, "I can see when I go for a walk at night with my mum." Andeep says, "Well, that's because there's some light coming from the streetlights." There you can see an image of some streetlights going down the road there.

If there is no light at all, then we cannot see another image of no light at all.

Can you think of a time when you were in a place with no light at all? Have a think.

Restart the video when you've done that.

Well, was there a time when you were in a place with no light at all? I wonder what you thought of.

Let's stop and think.

Which of these statements is true? We can't see when there's no light, it's dark when there is no light, or we can see a little when there's no light.

The correct answers here is A and B.

It is very dark when there's no light, and we can't see at all when there's no light.

When there is no light, we call this darkness.

Darkness, absolute darkness.

There are very few places on Earth where it is really dark like this.

There are very few places on Earth where it is dark in this way.

Can you think of any at all? Pause the video here and discuss.

Remember, we're not just talking about it being a little bit dark when you go to bed or at nighttime, because there is still sometimes a little bit of light in those times.

We're talking about a time when there is no light whatsoever.

Places where there are very few humans, and where there is no light, can be dark.

A torch is needed to see inside a cave, for example, because there is no light.

As you go further under the sea, there is less and less light, so it becomes harder to see.

In the very deepest parts, there is no light and it's dark.

It's very rare for us to be in the dark, as it is often so light around us.

I've got lights in my room here, and I can see all around me here.

If I turn the lights off, it's harder to see, but I can still see things.

There are ways of stopping light from reaching our eyes at all.

Can you think of any? Pause the video and discuss.

I wonder what you thought of.

Did you think of wearing a sleep mask at night, or maybe even putting on a blindfold to play a game? These are both instances of where we can stop the light reaching our eyes.

But I would think it would depend on the thickness of the material.

If the material is not very thick, some light will be able to seep through, and we can see slightly.

Laura says, "Well, when I close my eyes, I can't see." Here's an image of someone with their eyes closed, just like me.

Jacob says, "That's because our eyelids are opaque.

They don't let any light through, so we can't see when our eyes are closed." So by closing your eyelids, it means that you can't see light at all.

Your eyelids are completely opaque.

Our eyes need light to be able to see objects.

It's more difficult to see things in the dark, because there is less light.

Just like in that image there, it's very hard to see objects when there's less light, even though there are a few lights dotted around.

Jacob says," We might think it's dark, but there's usually some light from a light source somewhere helping us to see when you are walking along, for example." If you're outside in the woods, that might be coming from the moon or the stars at night.

What other items we can think of that might help us to see at night? Let's stop and think.

When it's dark, there is a lot of light, a little light, or no light? When it's dark, there is no light whatsoever.

So here is task A.

You need to design or make a dark den.

There must be no light in the den whatsoever.

That will enable you to not be able to see anything at all.

So what type of materials could you use to block out as much light as possible? Here you can see an example of a den.

Have a go planning your dark den now.

Restart the video when you've done that.

Good luck.

Well, I hope you didn't get lost in the dark den yourself.

Here we have Alex, who's had a go at designing and making a dark den.

He said, "We used opaque materials, like thick blankets and plastic, to design our den to block out as much light as possible." Here you can see Alex's dark den design.

He's got blankets right down to the floor so no light can come underneath.

He's got a table there that he's using as a bit of a structure, and they're gonna overlap some blankets for a door.

If they've got layers of thick blankets and a tarpaulin, that's gonna hopefully cut out the light completely.

Alex also says, "It was very difficult to make it dark inside the den.

Even with the blanket doors overlapping, we could still see some things, which meant that light was still getting in." Hmm, I wonder if the blankets they used were thick enough in this case.

I wonder.

How did you get on with your den designing? And hopefully you didn't get too lost inside the dark den.

The next part of this lesson is called using other senses.

The children start to move through to the next section of the dark cave.

Lucas says, "Well, I still can't see anything." Alex says, "I'm using my skin to feel my way along the rocks," and Sofia says, "I'm using my ears to listen and follow the sound of your voice." Moving around in dark places can be very dangerous, so I hope that the children are being careful in this case.

Not everyone has got a sense of sight.

Some people are born blind or partially sighted, and they're not able to see clearly, or at all.

They might need to use other senses, such as touch, to interact with the world around them.

You can use touch when walking using a stick, or you can use touch to read.

Both of these are ways that people who are blind or partially sighted can make sense of the world around them.

People who have little or no sight can use their sense of hearing to listen to audiobooks, and use technology to create talking labels for items such as food.

Here you can see some jars of food, and somebody who's partially sighted may have different labels on them, and use a device to be able to scan them, and that will tell them what they're looking at.

You may have seen a guide dog, like in this picture here.

Some people who are blind or have little sight may also use a guide dog to be able to help them to be independent.

Their guide dog can help them to walk safely to different places, avoiding obstacles and other dangers.

Stop and think.

Who do you agree with here? Lucas says, "When there's no light, we have to wait until our eyes get used to the dark, and then we are able to see." Alex says, "When there's no light, we can still use our eyes to see." And Sofia says, "When there's no light, we can use other senses, such as touch and hearing, to help us." Which of these statements do you agree with? Discuss.

Statement that I would agree with more here, is Sofia.

When there's no light, we can use other senses, such as touch and hearing, to help us.

Definitely.

Alex says, "We can still use our eyes to see when there's no light." Well, no, because there's no light.

Our eyes need light to be able to see, and although that your eyes might adjust in some darkened areas, when there is no light whatsoever, your eyes are never going to adjust to the dark.

So here is task B.

You need to design and make a very simple obstacle course to guide a partner, who will be wearing a blindfold, around.

You can only use verbal instructions here.

Try the obstacle course for yourself first, just to make sure that you can test it, and make sure that it's not going to be dangerous.

I wonder what other senses you are going to use when you can't use your sense of sight.

Remember, it's not just about putting your hands over your eyes.

If someone is blind, or partially sighted, they are not able to see very well at all, so they need to use different senses to help them get around.

So when you're trying this task, although it is gonna be very tempting to want to have a peek under the blindfold, see if you can complete it by completely closing your eyes and trusting on your other senses.

It can be a very scary thing to do, but I think you'll enjoy the session more with that extra challenge of making sure that you can't see anything at all.

Best of luck with this challenge.

Have fun making your obstacle course and be careful with your partner as you're guiding them through.

See you in a moment.

How did you get on? Were you able to design and make your own simple obstacle course? What other senses did you think of that you were using? You can see Andeep and Izzy here have both got their blindfolds on.

Andeep says, "I had to use my sense of hearing and listen carefully to the instructions that my friend gave me." So listening to instructions, as well as items that are around you, is going to be really important here.

Izzy says, "I used my sense of touch to help me to find my way safely through the obstacles." So feeling around in this case is going to help as well.

People who are blind often use a stick, so if that stick knocks into something, they know that there is an obstacle there.

When you are out walking, I wonder if you can take a look at the pavement and see if there's anything that can help a blind person know that there is the edge of a road, or that maybe something else needs to be using that part of the path.

For example, at the edge of a path where it meets the road, often the curb is slightly dipped, or you might find that there are little paving slabs with different bubbles on.

That will help somebody who is blind run their stick across it and find out that, actually, that's somewhere that they need to stop and wait for the traffic to stop first before they cross the road.

Likewise too, you might find different bumps or grooves in the road, which are gonna help a blind person be able to find their way around by running their stick along.

And run their stick along a grooved section is gonna help them walk along it as well.

So let's summarise our lesson.

We use our eyes to be able to see objects.

We need light in order to see.

Darkness is when there is no light whatsoever.

We often need to rely on other senses when there is no light at all.

Here you can see an example of a streetlight.

Although it may look dark outside, it's not truly completely dark if you can still slightly see.

Your eyes can slowly adjust to darkened places.

But in a true darkened place, when there is no light at all, it will be impossible to see, and impossible for your eyes to readjust.

As I challenged you before, have a think about how a blind person might be able to walk along the street, or if you see anybody with a guide dog, or see anybody with a stick helping them to see, make sure that you give them plenty of space so that they can run their stick along the ground, and that their guide dog can do the important work of guiding that person.

Hopefully, you were able to completely cover your eyes and give yourself a sense of being in the dark in that way.

I wonder how you use your senses in this case to find your way around.

Hopefully you were able to find your way through an obstacle course.

I wonder if you made it any more difficult for yourself.

Well done for completing both of those tasks in this lesson.

My name is being Mr. Wilshire.

Thank you very much for listening.