Semicircular Refraction Dish

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 12 cm across and 2 cm 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.

Activity suggestions:

• 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

Helps you teach the following Next Generation Science Standards Student Performance Expectations:

• Waves and their Applications in Technologies for Information Transfer (PS4)
  The path that light travels can be traced as straight lines, except at surfaces between different transparent materials (e.g., air and water, air and glass) where the light path bends. (MS-PS4-2)
• Waves and their Applications in Technologies for Information Transfer (PS4)
  The path that light travels can be traced as straight lines, except at surfaces between different transparent materials (e.g., air and water, air and glass) where the light path bends. (MS-PS4-2)
  Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. (HS-PS4-1)
• Wave Properties (PS4.A)
  The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. (HS-PS4-1)