Why is localhost:2000 working, but not any directory behind it?

I am new to node.js and was following the code given in this tutorial given at the time 11:33 in order to get the code below. Can someone explain why the error is occurring and how to fix it?

Currently, when I try to access localhost:2000 it works. However, attempting to access http://localhost:2000/client/img/bob.img resulted in this error.

Cannot GET /client/img/bob.img

Current directory formatting is also specified by the video at 2:35

Tutorial: https://www.youtube.com/watch?v=PfSwUOBL1YQ

var express = require("express");
var app = express();
var serv = require("http").Server(app);

app.get('/',function(req, res){
    res.sendFile(__dirname + "/client/index.html")


app.use("/client", express.static(__dirname + "/client/index.html"));

serv.listen(2000);

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