= Half-value layer
{title2=$x_{1/2}=\ln 2/\mu$}
{wiki}
The <half-value layer> is the thickness reducing the specified transmitted signal by one half. For constant monoenergetic <linear attenuation coefficient> $\mu$, solving $e^{-\mu x_{1/2}}=1/2$ gives $x_{1/2}=\ln2/\mu$. The stipulated $\mu=0.40\,\mathrm{mm^{-1}}$ gives $x_{1/2}\simeq1.73\,\mathrm{mm}$; two such layers transmit one quarter. A broad <frequency spectrum> need not retain the same <half-value layer> after filtering.
Back to article page
