We observed that when light ray travels from air to the plastic rectangular block, the refracted ray bends towards the normal.When the light ray travels from plastic rectangular block to the air, the refracted ray bends away from the normal. It is observed that when the angle of incidence is at 0 degrees, there is no refraction.
Image of the rectangular block when the angle of incidence is set at 0 degrees.
We observed that when light ray travels from the plastic semi-circle block to air, the light ray bends away from the normal. This was seen for angle of incidence of 10 to 40 degrees.