enough to the speed of light and therefore its longitudinal coordinate is <span class="math notranslate nohighlight">\(z \approx ct\)</span>, and the momentum is <span class="math notranslate nohighlight">\(p_z \approx \gamma mc\)</span></p>
<div class="math notranslate nohighlight">
\[\frac {d \gamma} {dz} \approx \frac {eE_z} {mc ^ 2},\]</div>
<p>Then it is enough to integrate the function <span class="math notranslate nohighlight">\(E_z (z)\)</span> once.</p>
</div>
<div class="section" id="Solution-of-t