refraction -- when can you see past the label? 1. The problem statement, all variables and given/known data as shown in the figure. 2. Relevant equations n1sin1 = n2sin2 n1 and n2 represent the refractive indices of media 1 and 2 respectively 3. The attempt at a solution Critical angle for glass-air interface = arcsin(1/1.5) = 41.8 degree so,a = 12tanC = 10.7cm? I just guess...I am not sure about what the question is asking for... Does it mean,assume the observer's position doesn't change, he can see O before placing the circular label.And he couldn't see O after placing the circular label?