Edit and compile if you like:
% Author: Izaak Neutelings (December 2020)\documentclass[border=3pt,tikz]{standalone}\usepackage{tikz}\usetikzlibrary{arrows.meta} % for arrow size\tikzset{>=latex} % for LaTeX arrow head\colorlet{xcol}{blue!70!black}\colorlet{vcol}{green!60!black}\colorlet{myred}{red!70!black}\tikzstyle{vvec}=[->,vcol,very thick,line cap=round]\tikzstyle{myarr}=[-{Latex[length=3,width=2]},myred]\def\tick#1#2{\draw[thick] (#1) ++ (#2:0.1) --++ (#2-180:0.2)}\def\xpeak#1{{(0.21+#1)*\xmax}}\def\wave#1{\coordinate (F) at (\xpeak{#1},\ypeak);\draw[very thick,xcol](-0.08*\xmax,0) -- ({(0.06+#1)*\xmax},0) to[out=0,in=180,looseness=0.5] (F)to[out=0,in=180,looseness=0.6]++ (0.25*\xmax,-\ypeak) -- (0.94*\xmax,0);}\begin{document}% WAVE t = 0\def\xmax{4.2}\def\ymax{2.0}\def\ypeak{0.80*\ymax}\def\v{0.17*\xmax}\begin{tikzpicture}\draw[->,thick] (-0.1*\xmax,0) -- (\xmax,0) node[right=4,below left=1] {$x$};\draw[->,thick] (0,-0.1*\ymax) -- (0,\ymax) node[left=1] {$y$};\wave{0.0}\node[above=4,right=5] at (F) {$y(x,0)=f(x)$};%\node[left] at (0.97*\xmax,0.65*\ymax) {$t=0$};\tick{\xpeak{0.0},0}{90} node[scale=0.9,below=-1] {$a$};\draw[vvec] (F)++(-64:0.35*\ymax) --++ (\v,0) node[above right=-2] {$v$};\end{tikzpicture}% WAVE t = Delta t\begin{tikzpicture}\draw[->,thick] (-0.1*\xmax,0) -- (\xmax,0) node[right=4,below left=1] {$x$};\draw[->,thick] (0,-0.1*\ymax) -- (0,\ymax) node[left=1] {$y$};
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