Overview: Take your science skills into the kitchen. Turn ordinary chocolate into an edible optics demo that shows how diffraction works.

Supplies: Stove, double boiler, heat proof spatula, candy thermometer, diffraction sheets, silicon molds (optional), chocolate bars or melting chocolate

Objectives: Diffraction is the bending of light. We do not need to look through a diffraction sheet to see the bending. Light can bounce off of fine grooved surfaces to show us how each wavelength of light refracts off of the surface.


Setup:

  • If using molds, cut the diffraction sheets into pieces the size of the bottom of the molds. Place the diffraction pieces, diffraction side up, in the bottom of the mold
  • Divide your chocolate into thirds, 2/3 are for melting, 1/3 is for the tempering
  • Different chocolates have different tempering temperature, these temperatures are critical for proper tempering
  • Follow this video (starting at minute 20 for chocolate) on how to temper chocolate and create the diffraction pieces
  • If using molds, chocolate can be poured into molds quite easily

How to run the demo:

  • Pass out the chocolate and explain what they see.

Try this:

Follow the instructions in the video (starting at minute 7:40) to make diffractive candy


What’s Happening?

White light can be separated into all seven major colors of the complete spectrum or rainbow by using a diffraction grating. The grating separates light into colors as the light passes through the many fine slits of the grating. Each color travels at a different speed and therefore has a different angle of refraction when it hits the grating. Chocolate makes a reflection gratings. Along with chocolate, a compact disc also makes a good reflection grating. When light passes through a grating it is called a transmission grating. A transmission grating is what is used to make the diffractive chocolate. Diffractive candy is a transmission grating.


Learn more: (external links)