Luminous and non-luminous objects
In the dark we can see nothing. To see anything at all, light has to come from it into our eyes.
Luminous objects
Objects that give out light of their own — a candle flame, an electric bulb, the sun. We see them because their light comes straight to our eyes.
Non-luminous objects
Objects that give out no light. We see them because light from the sun or a lamp falls on them and is reflected into our eyes.
Figure to be added
A non-luminous object is seen only by the light it reflects. That is why a room full of furniture looks empty when the lights go out.