Why does reflectivity suddenly change around critical angle? For example, consider the situation when incident light travel in dielectrics A and go in to dielectric B. Assume the dielectric constant $\epsilon_A=2.25$ and $\epsilon_B=1.25$. Total internal reflection occur when incident angle is around 46,7 degree. I'm wondering why reflectivity arise so sharply and suddenly? The reflectiviy is almost 0 when incident angle < 30 degree. And suddenly arise around critical angle. This is weird.
P.S Sorry. I only focus on TM wave unconsciously.