Grade 8 Science - Light and Optics

How do we see?

PLATO

Plato, an early philosopher, believed that light was emitted from our eyes, which then gave us the ability to see. What is wrong with this idea? What would happen if light did come out of our eyes?

Light enters our eye through the iris. Light receptors at the back of the eye then send messages up to the brain, which then allows us to see. There are two types of receptors in the back of your eye: rods and cones.

Rods and Cones have two very different jobs in helping you see:

Rods: Are used to help us see in dim light
Cones: Help us see color, and fine detail. There are three types of cones with each one responsible for one color: red, green or blue.

Here is a link to a test for color blindness.
This link takes you to acompany website. The company has created sunglasses for colorblind people with special lenses. These lenses allow for them to see the colors that they cannot.

Did you know that about 8% of men,and 0.5% of women are color blind?

There are many different parts of the eye, all which contribute to our ability to see. Each part plays an important role.

Part of the Eye	Description
Cornea	It controls and vocuses the entry of light into the eye
Iris	Surrounds the cornea and provides a person's eye color. It is responsible for the amount of light getting into the eyeball.
Lens	The lens is within your eye, and is responsible for focusing light as it enters the eye. It is a concave lens.
Vitreous Humor	The transparent jelly-like substance that fills the eyeball. It is behind the lens
Aqueous Humor	A thin-watery fluid. It is present between the iris and the cornea.
Retina	A thin layer of tissue that lines the back of the eye on the inside. The purpose of the retina is to recieve light, and send it on to the brain
Optic Nerve	Sends messages to the brain
Lens	Helps to refract light to be focused on the retina. It is a transparent structure.It focuses light on the retina
Pupil	Opening to the inner eye.

After learning all of the parts of the eye, we will get to dissect one! This is an awesome experiment, as it lets you see all of the different parts of the eye.

If you would like the answers for the eye work sheet, click here!

When white light shines through a crystal, it creates a rainbow on the other side. This is because white light is made up of all the different colors of the rainbow. As shown by the light color wheel :