Learners shine the light of a laser pointer through sheets of fabric that all have a different number of threads per inch. By looking at the patterns created, learners calculate the wavelength of the laser. The kit for this activity is no longer available, but you can still complete it if you have four fabrics and you know how many threads per centimeter are in each fabric. This activity starts on p.6 of the manual. This manual contains four activities related to the Spectra: The Original Laser Superhero Force comic book published by the American Physical Society.