Unit 2

The Sense of Sight

Content Learning Goal

• We will learn three parts of the outer eye and three parts of the inner eye. We will learn how the eye uses those parts to see.

Language Learning Goal

Define:• Enter• Iris• Pupil• Eyelid• Image• Lens• Retina• Focus

The Sense of Sight

• Eyes are like very good cameras…they can see small things or very large, wide pictures.

The Outside of the Eye

• Eyes need just the right amount of light to be able to see.

• Get a mirror and look at your eyes.• Look at your iris – that is the big, colored

circle. What color is your iris?• Now look at the smaller black circle in the

Iris. That is called the pupil. The pupil is really a hole in the iris. Light enters through that hole.

Outer Eye Continued

• The iris is a muscle. It can make the pupil bigger or smaller. It does that to control the amount of light that enters the eye.

• One other part controls the amount of light that enters the eye…what part is that?

• Yes…the eyelid. It can be lowered to keep out light. It can be raised to let in more light.

Experiment 1

• What happens to the eye in dim light or bright light?

• Take the mirror and go to where the light is dim…look in the mirror…are your pupils big or small?

• Shine the flashlight on your face. The light near your eyes is now bright. Are the pupils big or small?

Observations

• Answer the Observation questions on Page 151 and the Conclusions questions as well.

Inside the Eye

• We see because light rays bounce of objects in the world. The light rays carry colors, shapes and textures. These form images in our minds to tell us what it is that we are looking at.

Inside the Eye…

• The light rays first enter our eyes through our pupils. Then, they travel through the lens. The lens gathers the light rays together and sends them to the back of the eyeball where they land on the retina. The retina is where images are formed.

Inside the Eye…• Just like a movie-screen image, the image on

the retina must be in focus. That is the job of the lens.

• The retina has thousands of nerve cells…these cells are sensitive to light. Each cell senses a part of the image and sends a message to the brain. These messages are sent along the optic nerve.

• Your brain gets the messages and puts them together to make a mental picture of what you are seeing.

How the Sense of Sight Works

• Look at the Diagram on Page 153 and answer the 4 questions together in class

Experiment 3 – Page 156

• You have two eyes that each take pictures of what you see. Your brain takes the pictures from both eyes to figure out what you are seeing. You see better with two eyes than with just one.

• Get a pen with a cap and get ready for an experiment…Follow Steps 1, 2 and 3 on Pages 156-157.

Observations

• Answer the Observation question and the Conclusion questions on Page 157.

Review

• Complete Questions 1-7 on Page 158 on all we have learned about eyes.