Refraction of light — Describe

Describe an experiment to investigate the refraction of light through transparent blocks of different shapes.

Direct a ray of light from a ray box at an angle onto the flat face of a transparent block (e.g. rectangular, semicircular or triangular) resting on paper, and mark the paths of the incident and emergent rays with pencil dots. After removing the block, join the dots to trace the ray's path and measure the angles of incidence and refraction from the normal at each boundary. For a rectangular block, the ray bends towards the normal on entering the glass and away from the normal on leaving, so the emergent ray is parallel to the original incident ray but displaced sideways.