deletions | additions       diff --git a/When_a_laser_beam_of__1.tex b/When_a_laser_beam_of__1.tex  index ef33eec..bdc8567 100644  --- a/When_a_laser_beam_of__1.tex  +++ b/When_a_laser_beam_of__1.tex 
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\begin{equation}  \rho C \frac{\partial T}{\partial t} = k \nabla ^2 T + \gamma I  \end{equation}  where$c_k$ the thermal wave speed (usually taken as equal to the compression wave speed),  $\rho$ is  the density, $\kappa$ the thermal diffusivity and $C$ the heat capacity. The thermal diffusion path, equal to $\sqrt{4kt}$, where $k$ is ..., is equal to 0.01 $\mu$m.  
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