Cavity with a hole is a frequently cited approximation to a black body (more precisely, it is the hole that is the black body here):
Is there a simple estimate of how well such a cavity approximates black body? Presumably the parameters that matter are:
- the absorbance/reluctance of the inner surface of the cavity
- size of the cavity vs. the size of the hole
- shape of the cavity (including the shape of the opening, which could be a simple hole, a tube or even a system of lenses)
Ideally, I would like to see an equation relating the parameters of the cavity to the absorbance of the hole, or to how well the radiation emitted by the cavity approximates the black body spectrum.
Related
Trouble understanding the classic approximation of a black body as a hole on a cavity
I don't understand why a cavity with a hole is a black body
How can a cavity with perfectly reflecting walls approximate a perfectly absorbing black body?
