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The lens are this part that we see here. It's like something transparent, like a transparent crystal. It's the crystalline. Actually, we call it crystalline lens. It's like a transparent crystal where the light, the image passes through it and they project like a projector the image in this part of the eye. It is the back part of the eye.

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So when the light passes through the lens, they project the image here, but they project the image upside down. Look at this example. If you see here, these are the lens, the crystalline lens, and when the light passes through them, you see here there is a sunflower and some mountains.

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when the light passes through them, they project the image upside down in this part of the eye.

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If you remember from last year, we did an experiment about this.

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We explained last year that when the light passes through the magnifying glass,

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that is a transparent thing, it puts upside down. This is exactly the same that happens on your

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lens on your eyes. When the image passes through the lens of your eyes, it projects upside down

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into the back part of the eye or the retina, okay? So, if you have a magnifying glass, you can

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practice in your house, you can try. Here we have a window, okay? And here we have a magnifying glass

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And a piece of paper. And if you remember when you put the magnifying glass you see the street upside down. I don't know if you see very clear but through my window you can see a tree and a building but what you see on the image is upside down because if you look through the window properly you will see the building.

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okay so the lens have another very important function the first one is

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projecting the image in the eye but the second very important function is I want

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you to look at this part and see how they move and I want you to look at this

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image that they project in the back of the eye and see how the image changes

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Ready? As you can see, when the lens moves, I focus the image and I see properly or not.

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Do you see how the image changes depending on the shape of the lens?

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Depending on the shape of the lens, I see properly or not.

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Okay? So the lens projects the image in the back side of the eye and they focus and they allow you, they permit you to see properly. What happens if the lens don't work properly?

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If the lens don't work properly, you will probably need to put another lens, glasses, so you can correct and see properly and focus on the images that you see.

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Okay, these are the glasses. Let's see the example with this video. Okay, look. In this video, if you move the lens, you see how the light changes here and this is how you focus the image.

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Like this, you can see clear or not, okay?

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If your lens doesn't work properly, you need to put another lens like this to correct and see properly, okay?

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If you look at the next video, probably you will understand better.

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In this video, we see here the lens and the light passes through the lens and the image

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projects upside down in the retina.

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But if the lens is different and they don't have the correct shape, the image that you

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project is not going to be focused and you are going to see very bad.

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example like this. Okay, here as you can see we don't see properly because the

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image is projected here, but we put some glasses and now the image goes properly.

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Okay, this is just an example. This is another example of another lens that

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doesn't work properly you see here the image is not projected properly so we

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put some glasses and now we correct and we can see so these are the lens of your

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eye very important to focus the image