Light is central to all fields of science. It provides the energy that sustains life on Earth and powers numerous modern technologies, from lasers to fiber-optic communications. The United Nations Educational, Scientific and Cultural Organization (UNESCO) has declared 2015 the International Year of Light to promote global understanding of light and its many uses.
What is light, and where does it come from? Chemistry: Challenges and Solutions, unit 3, “Atoms and Light,” explains that light is electromagnetic radiation, or energy emitted from matter, and has many of the properties of waves. It introduces students to the electromagnetic spectrum, including many types of light that are invisible to the human eye, and to the idea that light can also have characteristics of particles. Physics classes can explore the wave-particle paradox in more depth in Physics for the 21st Century, unit 5, “The Quantum World.”
How does light produce color? Visible light looks white, but it contains the colors that we see in rainbows: red, orange, yellow, green, blue, indigo, and violet. Each color has a different wavelength, and the wavelengths can be separated by passing light through a prism. When light shines on an object’s surface, it absorbs some wavelengths and reflects others. The color we perceive is created by wavelengths of light reflecting from objects. Science in Focus: Shedding Light, workshop 4, “Colors, Cones, and Corneas,” explains how humans perceive color when light energy enters their eyes. To learn why different substances produce different colors, see Chemistry: Challenges and Solutions, unit 3, “Atoms and Light,” for information on spectroscopy and the emission spectrums of different elements.
Light powers many of the technologies that surround us. For example, a laser (Light Amplification by Stimulated Emission of Radiation) can cut materials as hard as wood or as soft as paper, read bar codes, and play music on CDs. Laserfest, a website commemorating the 50th anniversary of the laser’s invention, has images and videos that explain how lasers work and how we use them in its “About Lasers” section – including tips on laser pointer safety.
We can also learn about properties of light by looking outdoors at phenomena like rainbows and sunsets, which produce colors by refracting (bending light). The Northern Lights (Aurora Borealis) occurs when gaseous particles form Earth’s atmosphere collide with charged particles released from the sun’s atmosphere. “Light: Beyond the Bulb,” an open-source exhibition created for the International Year of Light, has an image gallery showing these and other examples of light in nature (click on the images for detailed captions).
How will you bring light into your science classroom?