如何让箭头更长

Question

我为一道光学问题画了下图。我想知道是否有办法让箭头线更长（用黄色高亮表示）。

有人可以建议如何实现这一点吗？

谢谢你！

\documentclass[]{article}
\usepackage[margin=0.5in]{geometry}
\usepackage{pgfplots}
\renewcommand{\thesection}{\arabic{section}}
\usepackage{mathtools}
\usepackage{cancel}
\usepackage{pgfplots}
\usepackage{amsmath}
\newtheorem{theorem}{THEOREM}
\newtheorem{proof}{PROOF}
\usepackage{tikz}
\usepackage{amssymb}
\usetikzlibrary{patterns}
\usepackage{fancyhdr}
\usepackage{bigints}
\usepackage{color}
\usepackage{tcolorbox}
\usepackage{color,xcolor}
\usepackage{booktabs,array}
\usepackage{hyperref}
\usepackage{graphicx}
\usetikzlibrary{arrows}
\usepackage{polynom}
\usepackage{wallpaper}
\usepackage{flexisym}
\usepackage{caption}
\usetikzlibrary{calc}
\usetikzlibrary{shapes.misc}
\usetikzlibrary{arrows}
\usepgfplotslibrary{fillbetween}
\usepgfplotslibrary{statistics}
\newenvironment{tightcenter}{
\setlength\topsep{0pt}
\setlength\parskip{0pt}
\begin{center}}{\end{center}}
\begin{document}
\begin{tikzpicture}
\draw[thick](-1.5,-2.0) -- (-1.5,2.0);  
%
\draw[thick](-3.2,-2.0) -- (-1.5,-0.5) -- (-3.2,1.0); 
\draw[thick](-3.2,-1.4) -- (-1.5,+0.1) -- (-3.2,1.6); 
\draw[thick](-3.2,-0.8) -- (-1.5,+0.7) -- (-3.2,2.2); 
%
\draw[thick,->](-3.2,-2.0) -- (-2.5,-1.38);
\draw[thick,->](-3.2,-1.4) -- (-2.5,-0.78);
\draw[thick,->](-3.2,-0.8) -- (-2.5,-0.18);
%
%
\draw[thick,->](-1.5,-0.5) -- (-2.7,0.56); 
\draw[thick,->](-1.5,+0.1) -- (-2.7,1.16); 
\draw[thick,->](-1.5,+0.7) -- (-2.7,1.76); 
\end{tikzpicture}
\end{document}

Answer 1

通过使用库arrows.meta和decorations.markings：

\documentclass[border=3.141592]{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows.meta, 
                decorations.markings}

\begin{document}
    \begin{tikzpicture}[
->-/.style = {thick, 
              decoration={markings,% switch on markings
              mark=between positions .2 and .8 step 0.6 with {\arrow[thick]{Straight Barb[scale=1.5]}}},
              postaction={decorate}
             }
                        ]
\draw[thick](-1.5,-2.0) -- (-1.5,2.0);
%
\draw[->-]  (-3.2,-2.0) -- (-1.5,-0.5) -- (-3.2,1.0);
\draw[->-]  (-3.2,-1.4) -- (-1.5,+0.1) -- (-3.2,1.6);
\draw[->-]  (-3.2,-0.8) -- (-1.5,+0.7) -- (-3.2,2.2);
    \end{tikzpicture}
\end{document}