I'm reading Randall Munroe's book How To: Absurd Scientific Advice for Common Real-World Problems. I probably don't have to tell you this, but it's awesome (as is everything from Randall Munroe, the ...

Plot a graph of sine of angle of incidence (y axis) against sine of angle of refraction. The gradient of this graph is the refractive index of the material of the semicircular block. So the ray ...