A luminous objects is one that is a source of light. A non-luminous object is one that reflects light from another source.
Colour
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How do we see colours? a coloured object will absorb all the colours of the spectrum apart from its own, and reflects that colour. So a green ball will reflect the green light and absorb all the rest of the colours. Black however, absorbs all the colours of the spectrum, so where you see a black object you are actually seeing an absence of light.
Primary Colours
Red, Yellow, Blue
Refraction
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Refraction is when light is bent. when rays of light enter something more dense than air, they slow down and refract towards the normal line. this is why a pencil in water looks bent.