We observed that when light ray travels from air to the plastic rectangular block, it bends towards the normal. This is because the light travels from a less dense medium to a denser medium. When the light ray travels from plastic to air, the light bends to its normal angle which is away from the medium. This is because the light moves from a denser medium to a less dense medium. We also observed that at angle 90 degrees, there is no refraction.
We observed that there is no longer any refraction when the angle of reflection is 45 degrees.