Objects that emit their own light are called luminous objects. Human eye perceives the light reflecting from different objects to cause the sensation of vision. In order to reflect from different objects, we must make the light to fall on the objects. Light is generated only from luminous objects. So luminous objects are responsible for our vision.
·Candle is a luminous object. But the earth does not emit its own light; it just reflects the sun-light falling on it.