Investigate how light paths bend at surfaces between 2 different transparent materials. Use this low-cost tool to create an engaging hands-on lab about wave properties and refraction. Fill the easy-to-clean dish with a common liquid then calculate its refractive index. Compare the results to known values to check accuracy. Plastic semicircular dish measures 12 cm across and 2 cm deep. Materials needed but not supplied include common liquids, straight pins or lasers, and protractors.