(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I just got a correct answer to a problem using the equation for the distance a density will propagate in time t below. Does anyone know where this comes from? I've already solved the homework problem, I just am not comfortable without understanding where this came from.

2. Relevant equations

[tex]x = 2 \sqrt{D t}[/tex]

Where x is the distance the density has propagated.

3. The attempt at a solution

So the diffusion equation can be solved for a 1-d situation giving (according to wikipedia I admit)

[tex]n=n_{0}erfc(\frac{x}{2\sqrt{D t}})[/tex]

Where erfc is the complementary error function, not sure how to make that look better in tex. Essentially to come up with the equation for diffusion length, the argument of erfc must be equal to 1. But I can't find a way to convince myself that is the case. Can anyone shed some light on this? Or maybe I'm way off, any help would be appreciated.

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# Homework Help: Distance a density will propagate in time

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