Describe the glass-block refraction experiment and a Snell-law check.

Solution & explanation

Trace a block on paper, mark entry and exit points with a ray box, and draw normals. Measure i and r from the same entry normal for several oblique rays. Calculate sin i/sin r for air-to-glass; it should be approximately constant within uncertainty. Parallel slab faces give a laterally displaced emerging ray parallel to the incident one; avoid measuring angles from the surface.