# Week 5: Eyes

This week's missions are all to do with your eyes and how they work! We'll be finding out all about eyes with the help of Professor Hallux and Nurse Nanobot!

# Mission 5: How Do We See In 3D?

All this week we're completing missions about the human eye with some help from Professor Hallux! Today we're looking at how our eyes see in 3D...

## Who is Professor Hallux?

Professor Hallux is a scientist who is really curious about everything to do with the human body!

With the help of Nurse Nanobot he wants to find out everything he can about how the human body works.

## Watch this video in which Professor Hallux and Nurse Nanobot find out about how we see in 3D…

After that you should have a good idea of how we see in 3D.

## What is 3D?

3D stands for 3 Dimensions.

We see in these 3 dimensions all the time without even thinking about it, not just when you watch a 3D film!

## What are the 3 dimensions?

They are length, width and depth.

When you watch a TV on a flat screen you are only seeing 2 – or 2D. The screen has length and width but no depth.

## What makes 3D better then 2D?

3D is so great because it allows us to see depth as this is one of the 3 dimensions.

Our ability to see depth is called Depth Perception and this allows us to to sense how close or far away things are to us.

## How do we see in 3D?

Because we have 2 eyes.

Each of your eyes is in a slightly different position which means that they each get a slightly different image that they send to your brain.

Your brain then uses information about the difference between these 2 images to work out depth.

## So how do they make it look 3D in the cinema if we’re just looking at a flat screen?

They do it by separating the image on screen into two slightly different images like this.

If you’ve ever taken your glasses off while watching a 3D film in the cinema you’ll see a blurry image a little bit like that one – it’s because you’re looking at these two slightly different images that are on top of each other.

The left and right lenses of your 3D glasses are different and can only see 1 of the 2 images on the screen. This means that your brain gets 2 separate images just like when you look at something in real life.

It’s the difference between these 2 images that makes it look like it has depth.

So we now understand what seeing in 3D is and how it helps us to tell how far away things are from us, let’s put that to the test!

Take 2 coins and hold them a few inches apart.

Now bring them together so that the edges touch.

Easy right?!

Now try it again but this time close one of your eyes.

It’s much harder right? It might have even taken you a few goes to do it. That’s because your brain only had one image from your eyes so it had trouble telling how far away the coins were.