What difference do you notice in refracted rays between the following figures?

What difference do you notice in refracted rays between the following figures ? What could be the reasons for that difference ?

In above both figures incident ray travels parallel to principal axis and we notice

  1. In figure (a) ray passing from rarer to denser medium, striking at convex surface and bends towards normal.
  2. In figure (b) ray passing from denser to rarer, striking at curved surface and be ids away from the normal.