Optically thin medium
= Optically thin medium
An optically thin medium has $\tau\ll1$, so attenuation and emission may be expanded to first order in optical depth.
= Optically thin
{synonym}
= Optically thin medium
An optically thin medium has $\tau\ll1$, so attenuation and emission may be expanded to first order in optical depth.
= Optically thin
{synonym}