Mean free path in units g/cm^2

[go quantum!]

Hello. I have just read a mean free path (a distance) written in units g/cm^2. How do you interpret this unit in terms of the usual idea of the mean free path as a distance?

 

[chrisbaird]

It looks more like a mean free path density than strictly a mean free path: (cm)x(g/cm^3). This would make sense because finding the mean involves averaging over many objects.