Consider the optical interface between crown glass and ethanol. Under what conditions would total internal relfection be possible at this interface? ilustrate your answer with a light ray diagram.

Okay so you need the angle of incidenc to be greater than the critical angle AND the light must be travelling from a medium of higher index refraction into a medium of lower index of refraction.
Im just confused with the diagram part.
I have my axis drawn, with crown glass on top since its higher index of refraction, and then water below. But now I don't know how to draw the arrow.

2 answers

draw the normal. then, the light in starting from inside the glass, traveling at the angle of incidence, hits the alcohol/glass interface, then is refraced from the normal 90 degrees (tangent to the interface). The incident angle in the glass (measured to the normal) is the critical angle.
so, both arrows should remain on the crown glass side of the axis, correct? t should just sort of look like a "V"?