How does vision work?

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.

Click on [next-image] to progress through the animation.