Tiks cavity & medium drawing

main.tex

\documentclass{article}
\usepackage{tikz}
\usepackage{mathtools}

\begin{document}

\begin{tikzpicture}

  \foreach \x in {140,143,...,210} {
    \draw[line width=1mm, shift={(2.5, 0)}] (\x:8) arc (\x - 40:\x - 20:5);
  }

  \draw[line width=1mm, shift={(-3.6, 5.15)}] (0,0) arc (140:210:8);

  \foreach \x in {30,27,...,-40} {
    \draw[line width=1mm, shift={(-2.5, 0.4)}] (\x:8) arc (\x - 40:\x - 20:5);
  }

  \draw[line width=1mm, shift={(4.4, 4.4)}] (0,0) arc (30:-40:8);

  \begin{scope}[shift={(0, -0.6)}]
    \draw[line width=1mm] (-2,-1) rectangle (2,2);
    \node at (-0.88,0.5) {\huge Active};
    \node at (-0.6,-0.27) {\huge Medium};
  \end{scope}

  \draw[->, line width=1mm] (0,-7) -- (6,-7);

  \draw[->, line width=1mm] (0,-7) -- (-6,-7);

  \node[scale=1.5] at (0, -6.2) {\huge $\ell$};

  \node[scale=1.5] at (-3.5, -5.5) {\huge $R_1$};

  \node[scale=1.5] at (3.5, -5.5) {\huge $R_1$};

  \node[scale=1.5] at (2.5, 5.5) {\huge Cavity};

  \draw[->, line width=1mm] (2.5,4.8) -- (1.75,3.1);

\end{tikzpicture}

\end{document}