This semicircular refraction dish is an economical way to open discussions and create hands-on labs about light waves and their properties. Fill the easy-to-clean dish with a liquid such as water, olive oil, or ethanol. Have students calculate the refractive index of each, compare their results, then check their data against known values for accuracy. To be successful with the activity, students need a basic understanding of geometry and trigonometry for a right triangle.
Plastic semicircular dish measures 12cm across and 2cm deep. Materials needed but not supplied include common liquids, straight pins or lasers, and protractors. Common classroom supplies such as rulers, paper (plain or polar graphing), and pens are also needed. Extend the activity by substituting a lens or prism for the liquid-filled dish or by using a laser line to replace the line of sight/straight pin measurement. Take care when selecting liquids, as some may react with the dish.
- Identify an unknown liquid by refractive index
- Investigate the relationship between refractive index and solution concentration
- Calculate percent error between experimental refractive index and the accepted value