Photon energy fluence
= Photon energy fluence
{title2=$\Psi$}
Energy carried by incident <photons> per unit area. For monoenergetic <photons>, $\Psi=E_\gamma\Phi$, where $\Phi$ is <photon fluence>. With <charged-particle equilibrium>, $D=\Psi\mu_{\rm en}/\rho$ relates it to <absorbed dose>.