Question

why do black boards appear black ?​

Answer 1

Answer:

Actually a black board has all colours in light or white light . So when light falls on it board absorbs all colours because all are present so no light is reflected back . That is the case when board has all colours and so it will appear black as it absorbs all colours of light that fall on it .

Answer 2

Then don’t appear in any other colour than black because, black and white are universal best contrasting colours.
Scientifically, black board don’t reflect much of the light, hence is easy to see what of written of the board.