why is it necessary that if there is no light reaching our eyes then we see black....
Answers
If black absorbs all light, then how do we see the colour black, because we see things by the reflection of light?
Colour is basically a sensation produced in our brain. It is not an actual thing. This is a very important concept that you need to remember.
Whenever an object reflects light, it appears coloured. For example if your table reflects blue light, it appears blue. Similarly, if it appears white, it means that it is reflecting all the colours of the visible spectrum(VIBGYOR). Since all the colours do not produce any specific sensation, the colour perceived is white.
Similarly, if an object reflects no light at all, no light reaches the eyes and the colour perceived is black. You can say in a way that the brain gets confused looking at no colour reaching the eye and hence it perceives black.
Feel free to leave a comment if you have any kind of doubt.
Thanks :)