Here's how it works:

1. Light source: A luminous object, like the sun or a light bulb, emits light.

2. Reflection: This light travels in straight lines and strikes the non-luminous object. The object's surface absorbs some of the light and reflects the rest.

3. Scattering: The reflected light scatters in various directions.

4. Eye detection: Some of this scattered light enters our eyes.

5. Brain interpretation: Our brain interprets the pattern of light entering our eyes and creates an image of the object.

In short, we see non-luminous objects because they act as mirrors, reflecting light from a source to our eyes.

Here's an example:

* You see a book on a table because sunlight or artificial light reflects off the book's surface and into your eyes.

Key takeaway: We don't actually see the object itself, but rather the light that it reflects.