Two options are suggested for how to conduct this activity. Option 1—When Silicon Talks, requires a silicon thin film, which is not available for public purchase, and is likely only accessible through a partnership with a research university. If this material cannot be acquired, follow the alternate Option 2—When Thin Film Talks procedure, which uses more readily available materials.

For Option 1—When Silicon Talks, each group needs:

• a sample single-layer porous silicon thin film, which is not available for public purchase but may be available by donation from universities with photonics laboratories; contact physics, electrical engineering and/or chemistry departments at any major university to inquire; if it is not possible to acquire this material, gather the Option 2 materials and follow the Option 2 procedure instead
• Measuring Refraction: Silicon Worksheet, one per student

For Option 1—When Silicon Talks, to share with the entire class:

• (optional) Ocean Optics Spectrometer that is capable of measuring reflectance in the visible range; a complete kit including spectrometer, light source and fiber optic cable is ~$4,000 new; used systems may be available for less; specific pricing varies since kits are assembled individually; contact Ocean Optics service representatives listed at http://www.oceanoptics.com/contact/
• (optional) computer or laptop with SpectraSuite® software installed, and a USB cable to the spectrometer; a modular, Java-based spectroscopy software platform that operates on 32- and 64-bit Windows, Macintosh and Linux operating systems to control any Ocean Optics USB spectrometer; available from Ocean Optics, same details apply as with the spectrometer; old software versions may be available for free upon request
• Alternative: If a spectrometer with computer and software is not available, use the Screen Captures of Spectrometer Images as an overhead projector visual aid and/or group handout
• classroom projector
• tweezers, for handling the silicon samples
• (optional) clamp, to secure the fiber optic cable

For Option 2—When Thin Film Talks, each group needs:

• 4 pieces black construction paper
• 1 disposable plastic or aluminum tray, such as a disposable litter tray for $3.28 each at Walmart
• 1 bottle clear nail polish, such as Sally Hansen brand for $2.97 per bottle at Walmart
• 1 plastic transfer pipet, such as 3-ml graduated plastic transfer pipet, 20 for $4.76 at https://www.amazon.com/Rienar-Disposable-Transfer-Graduated-Pipettes/dp/B00P7QZDK4/ref=sr_1_1?ie=UTF8&qid=1512079406&sr=8-1&keywords=3-ml+graduated+plastic+transfer+pipet
• 1 plastic fork
• 4 paper towels
• personal protective equipment: gloves, goggles, well-ventilated lab area
• Measuring Refraction: Thin Films Worksheet, one per student
• classroom projector
• access to water