Expected behavior of adjusting the fresnell power is that the faces towards the camera should become darker and faces at an angle from camera should remain coloured with the diffuse color. This is not what happens as if the opacity is set to 100, the fresnell power and index of refraction have no effect on rendering. Only when the opacity is dropped to really low (around 16) you start to see the fresnell effect in the rendering.

There should be no dependency between fresnell power & index of refraction and opacity.