How does vision work?

Learning objectives

To apply the linear ray model of light.
To understand that light has to enter the eye, and that the object being observed must itself be receiving sufficient light from a primary source.
To show that the eyes are only light receptors. The brain is the interpreter that enables vision to occur.
To show that light is everywhere around us. Only the tiny part of it penetrating our eyes participates in vision.

To see, enough light must go into the eye. In general, the light that propagates from the source to the object and then from the object to the source is invisible.

The objects that are seen in this way are secondary sources. In contrast, the light bulb that illuminates the scene is a primary source.

The eye and the brain are both involved in the vision process.

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