How we see

In a nutshell

You can see objects because they are a source and pass light directly into the eyes, or because they reflect light from a source into your eyes.

How objects are seen

There are two situations in which we can see the objects around us. These are:

The object is a source and passes the light directly into the eyes.
The object is not a source, but it reflects light from another source (such as the Sun) and into the eyes.

A light source is an object which produces light. This means that if an object is not a source, then it does not produce its own light.

Example:

A source is a fire or a glow stick. Bike reflectors are not a source of light.

The eye

The eye is very important for focusing light in order to see. Objects are seen because they produce or reflect light that travels into the eye. The lens in the eye focuses the light onto the retina.

1.	Object
2.	Pupil
3.	Iris
4.	Lens
5.	Retina
6.	Optic Nerve

Once the light enters the eye, a message is sent to the brain via the optic nerve, and the brain interprets what it is seeing.

Curiosity: Someone may need glasses to see because the light doesn't focus properly on the retina.