The two cars illuminated by sodium lamps appear black because the red and black colours are absorbed and no colour is reflected.
Reflection of light is the ability of light rays to bounce back off a surface when they are incident on that surface
The ability of light to be reflected gives rise to changes in the colour of objects
When light is incident on a surface, the colour that is reflected gives the colour of that object.
Therefore, when two cars of red and black colur are illuminated by sodium lamps, they appear black because the red and black colours are absorbed and no colour is reflected.
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