hey so i'm doing this question on total internal reflection and have got myself totally lost here is the question: what is the smallest angle [tex]\theta[/tex](1) for which a laser beam will undergo TIR on the hypotenus of this glass prism? after reflecting off the hypotenuse at [tex]\theta[/tex](c) the laser exits the prism through the bottom face. does it exit to the right or left of the normal? at what angle? http://photos-603.facebook.com/n11/161/86/37900227/n37900227_30061603_2132.jpg [Broken] that is a picture of what is going on here Now, i realize that at some point im going to be using snells law as well as the equation for critical angle. My question is.. what do I do? I am totally lost as you can probably see, and any help would be much appreciated thank you twiztidmxcn *edit* i've used the critical angle equation and found that the critical angle is 41.81 degrees (using n1 = 1.5 for glass, n2 = 1.0 for air) and didn't know what to do with it... i ended up subtracting the triangle angle of 30 degrees and setting 1.5*sin11.81 = 1*sin theta and solved for theta. i got the right answer, but am not sure how the 30 degrees is subtracted. i know it involves similar triangles but am just not seeing it i guess. same for the second part, i just subtracted 60-41.81 and then setup the same equation to find my angle coming out, which again i got correct, but am stumped as to how that works.