 | metal | glass

back &lt;-<span class="st"> </span><span class="kw">list</span>(<span class="dt">wavelength=</span><span class="fl">632.8</span>,
             <span class="dt">angle =</span> <span class="kw">seq</span>(-pi/<span class="dv">2</span>, pi/<span class="dv">2</span>, <span class="dt">length=</span><span class="fl">1e4</span>)[-<span class="kw">c</span>(<span class="dv">1</span>, <span class="fl">1e4</span>)], 
             <span class="dt">epsilon =</span> <span class="kw">list</span>(<span cl