how can the diffracted wave can be drawn?

Question

So I was preparing a lesson for my students about mechanical waves, and when I’ve reached the section of diffraction I needed to do some figures like these :

For the first one I’ve done it easily, and here’s the result :

and here’s the code :

begin{tikzpicture}[scale=0.8]
draw[smooth] (0,0)--(0,-6);
draw[smooth] (1,0)--(1,-6);
draw[smooth] (2,0)--(2,-6);
draw[smooth] (3,0)--(3,-6);
draw[smooth] (4,0)--(4,-6);
draw[ultra thick] (5,1)--(5,-2);
draw[ultra thick] (5,-3.5)--(5,-7);
draw[smooth,<->] (0.1,0)--(0.9,0) node[above, midway] {$lambda$};
draw[smooth] (6,-2)--(6,-3.5);
draw[smooth] (7,-2)--(7,-3.5);
draw[smooth] (8,-2)--(8,-3.5);
draw[smooth, <->] (6.1,-2)--(6.9,-2) node[above, midway] {$lambda$};
draw[smooth, ->] (5.5,-1)--(5.1,-1.9);
node[right] at (5.5,-0.9) {La fente $a$};
node[] at (5,1.4) {Figure $1$};
end{tikzpicture}

But I got some problems with the second figure, in the second part where the waves should be diffracted :
I can’t draw these arcs even I am using the arc code, I think I’m not understanding how it works :

begin{tikzpicture}
draw[smooth] (0,0)--(0,-6);
draw[smooth] (1,0)--(1,-6);
draw[smooth] (2,0)--(2,-6);
draw[smooth] (3,0)--(3,-6);
draw[smooth] (4,0)--(4,-6);
draw[ultra thick] (5,1)--(5,-2);
draw[ultra thick] (5,-3)--(5,-7);
draw[smooth,<->] (0.1,0)--(0.9,0) node[above, midway] {$lambda$};
draw[smooth, ->] (5,-1.9) arc (0:-50:3);
draw[smooth, ->] (5.5,-1)--(5.1,-1.9);
node[right] at (5.5,-0.9) {La fente $a$};
end{tikzpicture}

Any suggestions?

draw physics tikz pgf

js bibra · Accepted Answer

Something to get started

begin{tikzpicture}[scale=0.8]
    draw[smooth] (0,0)--(0,-6);
    draw[smooth] (1,0)--(1,-6);
    draw[smooth] (2,0)--(2,-6);
    draw[smooth] (3,0)--(3,-6);
    draw[smooth] (4,0)--(4,-6);
    draw[ultra thick] (5,1)--(5,-2);
    draw[ultra thick] (5,-3.5)--(5,-7);
    draw[smooth,<->] (0.1,0)--(0.9,0) node[above, midway] {$lambda$};
%   draw[smooth] (6,-2)--(6,-3.5);
%   draw[smooth] (7,-2)--(7,-3.5);
%   draw[smooth] (8,-2)--(8,-3.5);
%   draw[smooth, <->] (6.1,-2)--(6.9,-2) node[above, midway] {$lambda$};
%   draw[smooth, ->] (5.5,-1)--(5.1,-1.9);
%   node[right] at (5.5,-0.9) {La fente $a$};
    node[] at (5,1.4) {Figure $1$};
      defRadius{0.75}
    
    draw
    (5,-3.5) arc(-90:+90:Radius) -- cycle
    ;
end{tikzpicture}

and some more fine tuning

documentclass{article} % or another class
usepackage{xcolor} % before tikz or tkz-euclide if necessary

usepackage{tkz-euclide} % no need to load TikZ
begin{document}
begin{tikzpicture}[scale=0.8]
    draw[smooth] (0,0)--(0,-6);
    draw[smooth] (1,0)--(1,-6);
    draw[smooth] (2,0)--(2,-6);
    draw[smooth] (3,0)--(3,-6);
    draw[smooth] (4,0)--(4,-6);
    draw[ultra thick] (5,1)--(5,-2)coordinate(b);
    draw[ultra thick] (5,-3.5)coordinate(a)--(5,-7);
    draw[smooth,<->] (0.1,0)--(0.9,0) node[above, midway] {$lambda$};
    node[] at (5,1.4) {Figure $1$};
      defRadius{0.75}
    
    draw[blue,thick]
    (5,-3.5) arc(-90:+90:Radius) 
    ;
        draw[blue,thick]
    ($(5,-3.5)+(0,-0.5)$) arc(-90:+90:1.25) 
    ;
        draw[blue,thick]
    ($(5,-3.5)+(0,-1.5)$) arc(-90:+90:2.25) 
    ;
    draw[draw=none] (a)-- node[midway](b'){}(b);
    draw[ <->, red]($(b')+(1.25,0)$) --($(b')+(2.25,0)$)node[above, midway] {$lambda$};
    draw[->,red, thick]($(b')+(2.5,0)$) --($(b')+(3.5,0)$);
    draw[->,red, thick, rotate=45]($(b')+(2.5,0)$) --($(b')+(3.5,0)$);
    draw[->,red, thick, rotate=-45]($(b')+(2.5,0)$) --($(b')+(3.5,0)$);
    draw[<->,red, ](a) --(b)node[left, midway] {$a$};
end{tikzpicture}
end{document}

how can the diffracted wave can be drawn?

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