Seeing with light

Seeing luminous things

You can see things when light from them enters the eye. When light starts from the thing, that thing is called a luminous source. The Sun is a luminous source because light comes from it. Car headlamps, torches, and candle flames are also luminous.

Seeing non-luminous things

You can still see things when the light does not start from the thing. Light from a luminous source reflects from the thing, and your eye detects this reflected light. Now the thing you see is referred to as a 'non-luminous'.

Many everyday things are non-luminous sources. The table, a chair, the curtains, and that dog are all examples.

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