Shaded hollowed-out sphere

Example4.tex

\documentclass[crop=true, border=10pt]{standalone}

 
\usepackage{xcolor}

\usepackage{tikz}
\usetikzlibrary{arrows.meta}


% Some colors I like. The first six are modified versions of colors from
% the Gnome Project "Tango" palette.
\definecolor{plum}{rgb}{0.36078, 0.20784, 0.4}
\definecolor{chameleon}{rgb}{0.30588, 0.60392, 0.023529}
\definecolor{cornflower}{rgb}{0.12549, 0.29020, 0.52941}
\definecolor{scarlet}{rgb}{0.8, 0, 0}
\definecolor{brick}{rgb}{0.64314, 0, 0}
\definecolor{sunrise}{rgb}{0.80784, 0.36078, 0}
\definecolor{lightblue}{rgb}{0.15,0.35,0.75}
\definecolor{carolina}{RGB}{153, 186, 221}

% A custom arrowhead for use on x, y, z axes
\tikzstyle{axisarrow} = [-{Latex[inset=0pt,length=5pt]}]

\begin{document}

\begin{tikzpicture}[scale=1.2]
	% Draw the grid.
	\draw [cornflower!20,step=0.25,thin] (-3,-3) grid (3,3);
	\draw [cornflower!40,step=1.0,thin] (-3,-3) grid (3,3);

	% Draw the shaded region between the inner and outer radius
	\shade[shading=radial, inner color=white, outer color=orange!60!yellow, opacity=0.90] (0,0) circle (2cm);

	% Draw the hollow interior region
	\draw[black,fill=white] (0,0) circle (1cm); 
 
	% Foreground equator for inner sphere
    \draw (-1,0) arc (180:360:1cm and 0.3cm);
	% Background equator for inner sphere
    \draw[dashed] (-1,0) arc (180:0:1cm and 0.3cm);

	% Foreground equator for outer sphere
    \draw (-2,0) arc (180:360:2cm and 0.6cm);
	% Background equator for outer sphere
    \draw[dashed] (-2,0) arc (180:0:2cm and 0.6cm);
 
	% Outline the outer sphere 
 	\draw[black] (0,0) circle (2cm);
	
    % Define coords for endpoint of radial line for outer sphere.
    \pgfmathsetmacro\Rox{1.9*cos(50)};
    \pgfmathsetmacro\Roy{1.9*sin(50)};
	% Draw radial line
    \draw [dashed] (0,0)--(\Rox,\Roy);
	% Place outer radius label
	\node at (\Rox,\Roy) [xshift=0em, yshift=-1.5em] {$R_o$};

    % Define coords for endpoint of radial line for inner sphere.
    \pgfmathsetmacro\Rix{0.95*cos(140)};
    \pgfmathsetmacro\Riy{0.95*sin(140)};
	% Draw radial line
    \draw [dashed] (0,0)--(\Rix,\Riy);
	% Place inner radius label
	\node[fill=white,inner sep=0pt] at (\Rix,\Riy) [xshift=0em, yshift=-1em] {$R_i$};

	% Node with formula for charge density
	\node[inner sep=0pt] at (2.1,-1.8) [xshift=0em, yshift=0em] {$\displaystyle \rho = \frac{k}{r}$};

	% Arrow from charge density to region between inner and outer radius
	\draw[>={Latex[inset=0pt,length=5pt]}] (1.65,-1.85) edge[out=180,in=290,->] (.8,-1.2);
\end{tikzpicture}	

\end{document}