Another flamin' puzzle

[AlanMiller]

Here's something I was discussing at a recent lecture I gave:

Copy.jpg

Question:

Why is the lower edge of the metal bar visible through the outer region of the flame, but not through the inner region?

Alan

[Rudi]

My guess without Googling is, its either the fact that the hotter inner portion emits too much light that obscures the matter behind it, or the fact that the inner portion contains a much more dense population of gas molecules that make up the actual flame.

[AlanMiller]

My guess without Googling is, its either the fact that the hotter inner portion emits too much light that obscures the matter behind it, or the fact that the inner portion contains a much more dense population of gas molecules that make up the actual flame.

The first guess is interestingly close to the mark, and I hadn't thought of it in those terms. The density of the flame is probably near enough to uniform though. Certainly, the "hotter" reference is of great significance.

BTW, it's a tube - not a bar... before any pedant jumps in.

Alan

[Rudi]

...The density of the flame is probably near enough to uniform though...

Interesting comment... I didn't realize this?
I thought that the flame would be more dense in the middle!
So the only difference is heat?

[AlanMiller]

...The density of the flame is probably near enough to uniform though...

Interesting comment... I didn't realize this?
I thought that the flame would be more dense in the middle!
So the only difference is heat?

I can't be sure of the density comment. Point being that your comment about the hotter centre of the flame is of significance to the question.

Alan