Students will learn about how light interacts with matter at sub-wavelength length scales. When they complete the Activities, they will be ready for the Design Project in which they will fabricate, test, and evaluate their own photonic crystals.

By incorporating everyday materials into science lessons, the Materials World Modules (MWM) program at Northwestern University has found the solution to getting students excited about learning science while helping teachers meet national and state education standards.

The modules are easy to organize and inexpensive to run. They can be incorporated into any science class because of the breadth of subjects covered in the Activity and Design Project sections. Each module is a supplemental science unit that takes 1-3 weeks of class time (approximately 10 hours) to complete.

» Module At-a-Glance
» Connecting to Your Curriculum

Activity 1: Lights and Their Spectra
By examining the spectra of different light sources using the same diffraction grating, students will recognize that superficially similar light sources can have different results.

Activity 2: Observing Diffraction
When a wave encounters an object or edge similar in size to its wavelength, it will tend to bend, or diffract, around that object. This is a fundamental behavior of all waves. Students will observe the diffraction of various waves, including light.

Activity 3: Observing Interference
Interference results whenever two or more waves occupy the same space at the same time. Waves diffracting from two nearby coherent sources will generate patterns of interference. Students examine similarities and differences in the patterns generated by different types of waves.

Activity 4: Observing Iridescence
When white light is shone on objects that have structure on the same length scale as the wavelength of light the interference patterns created are different for each wavelength. This means each color will reflect, or not, at a different angle, leading to iridescence. Students explore several different examples of iridescence in both natural and manufactured objects and develop an understanding of how this effect occurs.

Design Project: Fabricating Photonic Crystals
Based on what they learned about light, diffraction, interference, and iridescence, students will model and then fabricate photonic crystals. They will also develop evaluation criteria and perform tests on their crystals, the results of which will be presented to the class.

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Materials World Modules are designed to be easily incorporated into any middle school science or high school science lab or lecture course. The chart below lists the subjects covered in the Activity and Design Project sections of this module.

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