Astronomers have spent thousands of years figuring out the best way to see, collect, and analyze the light that has spent millions and billions of years crossing the universe to reach our telescopes and cameras. But there is more to light than what can be sensed by the human eye. The microwaves that are emitted when you heat up your lunch, the ultraviolet rays that give you a sunburn, the X-rays that help doctors find broken bones, are all forms of light too. So, what exactly is this light that we spend so much effort gathering? Our first hands-on activity aims to begin building an understanding of the different forms of light in a way that doesn’t rely on visual graphics.
A core concept that we need to understand is that light is a wave. All the reds and greens and blues that the human eye can detect are waves, composed of electric and magnetic fields that weave together. In fact, there is a spectrum of these waves, from the longest radio waves to the extremely short gamma rays from solar flares. This is called the electromagnetic (EM) spectrum. At one end of the EM spectrum are radio waves. They have the longest wavelengths and the lowest of frequencies (the number of waves passing a point in a given time). Low frequency is associated with low energy waves on the EM spectrum. As wavelength decreases, we arrive at microwaves, then infrared, visible, UV, X-ray, and finally, the most energetic (shortest wavelength and highest frequency), gamma rays.
Often, this spectrum is represented as a visual graphic, showing a wave with its peaks spaced closer and closer together (i.e. decreasing in wavelength), with different parts of the wave labeled with their corresponding forms of light and associated properties. The goal of this activity was to turn this highly inaccessible, visual representation, into something that students can build and touch to understand the different parts of the EM spectrum and understand how key properties of frequency and wavelength are related.
Our EM spectrum is built from puzzle pieces that fit together in a line. Students form groups. Each group is in charge of one part of the EM spectrum, i.e. one puzzle piece. Every group has a certain thickness of string or yarn material (inversely representing the energy of the wave) and pushpins. They follow instructions to put in the correct number of pushpins in the right locations and string the yarn in a wave to create the correct number of peaks and troughs for each segment of the EM spectrum. Once all the pieces are assembled, the class works together to fit the entire spectrum in order, from longest to shortest wavelength or lowest to highest energy. In fact, you can have the students order the spectrum in different ways so they can investigate the relationship between frequency, energy, and wavelength.
We look forward to hearing your thoughts and comments!!