On 05/10/2020 18:49, williamwright wrote:
On 05/10/2020 12:28, JohnP wrote:
A black radiator gives off more heat.

Why should the efficiency of a surface in absorbing light affect its
efficiency in radiating heat?

Assuming the black is black in infrared too (it's possible, but
unlikely, it's black in visible and white in IR) then the black colour
is just one effect of a surface that is good at transferring radiation.

Both ways.

If you could have a surface that absorbed better than it radiated, or
vice versa, you'd have free heating (or cooling). TANSTAAFL.

Andy