Which color of a surface makes it better at emitting and absorbing infrared radiation, black or white?
So in this question we have to work out which color, whether it’s black or white, is the better color at emitting and absorbing infrared radiation. Now the first thing we need to know is that good absorbers of infrared are also good emitters of infrared. Therefore, any surface that’s good at absorbing infrared will also be good at emitting it.
Secondly, we need to know is that white surfaces reflect visible light and black surfaces absorb it. That’s actually the reason why these surfaces appear white or black, because white light is made up of all colors of the spectrum. So if we shine white light on a certain surface and it reflects it all back at us, then that surface will appear white to us, whereas if we shine some white light onto a surface and it absorbs all of the light, then we will see it as black.
However, this is only talking about visible light, not infrared. Now when it comes to white surfaces and black surfaces, they are both pretty decent absorbers of infrared radiation. However, black surfaces absorb most of the visible light that we shine onto them and a lot more infrared radiation that we shine onto them compared to white surfaces. The white surfaces are not quite as good as black surfaces at absorbing infrared radiation.
In other words, the black surface and white surface have absorption spectra that look like the following. The white surface shown above has some absorption in the infrared range and very little in the visible, because it reflects most of the light in the visible range, whereas the black surface has a lot of absorption in the infrared range and a lot of absorption in the visible range.
So a black surface is a better absorber of infrared radiation. And as we said earlier, good absorbers are good emitters and vice versa. So black surfaces are also better at emitting infrared radiation. Hence, our final answer is that black surfaces are better at emitting and absorbing infrared radiation.