I am trying to design a refraction lab involving the critical angle and I have an idea but i'm not sure if it is good or, for lack of a better word, stupid. Here it is: Using a laser and a rectangular container filled with water, I will shine the laser at the container and rotate the angle at which I shine it through. Then I will record the angle at which the laser no longer goes all the way through but reflects, or the critical angle. I will do this for 5 different substances with different indexes of refraction. Looking at the equation ni sin(i) = nr sin(r), I can plot ni vs sin(r), where r is the measured critical angles, because ni is air which is about 1. Then, the slope of this graph will be equal to sin(i). The slope is equal to 1 making the angle i 90 and proving the equation for the critical angle. I'm pretty sure the math is correct but overall, is this a nice lab proving a know equation or is stated in the definition of the critical angle that that angle is 90 and therefore this is a, for lack of a better word, stupid lab. Thanks for the help!