Definition:Density (Physics)/Area

Definition
The area density of a two-dimensional body is its mass per unit area.

The usual symbol used to denote area density is $\rho_A$, although some sources simply use $\rho$ if the context makes it clear that it refers to area density rather than volume density.

Occasionally, $\sigma$ (Greek letter sigma) is also used, but this is more commonly used for surface charge density.

Dimension of Area Density
The dimension of area density is $M L^{-2}$: mass per unit area.

Units of Area Density

 * The SI units of area density are $\mathrm {kg} \ \mathrm m^{-2}$ (kilograms per square metre).


 * The CGS units of density are $\mathrm g \ \mathrm{cm}^{-2}$ (grams per square centimetre).

Thus:
 * $1 \ \mathrm g \ \mathrm{cm}^{-2} = 10 \ \mathrm{kg} \ \mathrm m^{-2}$

Also known as
Also known as surface density, areal density or planar density.

Also see
Definition:Density (Physics) Definition:Linear Density