Science Questions

Is black a colour?

Tue, 4th Oct 2016

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Martin asked:

Hi. Is black really a colour ? Or just the absence of light ? (visible light)


We put Martin's question to Caroline Steel...Black

Caroline - Black is just the absence of light really. It sort of seems to be a colour to us because we can differentiate it from other colours, but a black object is actually an object that absorbs all colours of the visible spectrum, thatís all frequencies of light. So say this black microphone absorbs red, blue green, all of the colors, so to us it just looks like the absence of colour, which is black. So when we shut our eyes we see black as no lightís getting in.

The opposite of this would be white. A white object reflects all light and when we can see all frequencies of visible light, they combine to make sort of a white colour, although colour would be a slightly misleading word.

Chris - We had Pulickel Ajayan on the programme about 2008, I think it was. And he published this paper that said the new black, and said that heíd made the blackest substance ever made. And he sent me a picture of it and I actually had this disc of this stuff and the industry standard of what we call black. And his stuff, he says, is thirty times blacker than black. It seems paradoxical that something could be blacker than black, but it really was dramatically darker.

And their technique was exactly as you say Caroline. The reason something has a colour is because itís reflecting light off itís surface. His approach was well if we want to stop light being reflected off a surface - how do we do it. They made a layer of carbon and had this bamboo like forest of carbon nanotubes sticking up like bristles off of the surface. And their rationale was any photons of light that go in there will ricochet around and just get lost in these carbon nanotubes and never come out. It just basically turns the light into heat in the surface, and thatís why itís so black. But no, an amazing discovery.


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hmmmm.. i always thought black AND white were deemed not true colours and that black, as stated above, is the absence of the absorption of light.....which, i guess could well be assigned to as a colour  !

Lets hope a passing Colourologist provides some assistance here ! neilep, Tue, 20th Sep 2016

Black is the absence of visible light.
Adding any visible wavelengths to the light entering your eyes makes it non-black.

...and when they said "Orange is the new black", they weren't physicists saying it! evan_au, Tue, 20th Sep 2016

As stated above black is not a color but the absence of all light, i.e. the absence of color. White is a bit harder to say if it's a color. White light is a composed of a spectrum of other colors. That said, when a car dealer asks me what color I want my new car to be I'll always say "black." :) PmbPhy, Tue, 20th Sep 2016

In the 4 colour printing process 4 colour separations are produced Y,C,M,K(black)  and the black separation is printed with black ink and referred to as one of the 4 colours syhprum, Tue, 20th Sep 2016

In light the absence of all colors is black, in paint the presence of all colors is black, you decide. mrsmith2211, Wed, 21st Sep 2016

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