About Light Topics for Science

Light is everywhere in our world. We need it to see: it carries information from the world to our eyes and brains. Seeing colors and shapes is second nature to us, yet light is a perplexing phenomenon when we study it more closely.

Here are some things to think about:

Our brains and eyes act together to make extraordinary things happen in perception. Movies are sequences of still pictures. Magazine pictures are arrays of dots.

Light acts like particles—little light bullets—that stream from the source. This explains how shadows work.

Light also acts like waves—ripples in space—instead of bullets. This explains how rainbows work. In fact, light is both. This "wave-particle duality" is one of the most confusing—and wonderful—principles of physics.

Scientists have spent lifetimes developing consistent physical, biological, chemical, and mathematical explanations for these principles. But we can start on the road to deeper understanding without all the equations by acting as scientists do: making observations, performing experiments, and testing our conjectures against what we see.

The activities in this lab are designed to give you ideas about light—and also about how you can use technology to explore light. Collectively, the activities are a sampler—rather than comprehensive demonstration—of these two topics:

Light in Color. Color is more than decoration, and perceiving color is tricky. Three activities help you see how colors interact and how we can use color as a scientific tool.

Laws of Light. Light behaves according to special rules; for example, it usually travels in a straight line and it bounces off mirrors at the same angle it hits them.

In this lab, you will work with simulations to see things more quickly and conveniently. This has merit, but it's no substitute for the real thing. So, wherever possible, follow the links to hands-on activities. You will find many of these explanations in their original form at the Exploratorium.

Light is a wonderful subject for school study partly because you can teach some facet of it at every grade level.

Younger primary school students can compare their own shadows against themselves. You might ask them, How is your shadow like you? Is it taller or shorter or just the same height? These students can look in a mirror, raise their right hand, and answer the question, Which hand is the reflection raising? At this stage, they make only informal observations about light and color.

Slightly older students develop more sophisticated ideas about shadows. For example, when they are outside, they will see that the places in shadow are the ones from which they cannot see the sun. These students may also learn more formally about color; for example, remembering that blue and yellow make green when they are mixing pigments. They may also play more games with mirrors, especially in math class.

Students in the middle grades learn about prisms and spectra, and may informally study refraction (how the pencil seems to bend when it is put in water), more sophisticated reflection (why a right-angle mirror always reflects), and other physical properties of light (such as its momentum, as evidenced by the radiometer).

All of this prepares students to grasp the subject of light more formally: from calculating reflection angles to learning about energy transfer, the electromagnetic spectrum, the indices of refraction, the speed of light, and so forth.

In the National Science Education Standards (National Academy of Sciences, 1996), you can find many reasons to study light. Various aspects of this subject appear in the standards for physical science.

To begin, you will need to engage students actively in doing scientific inquiry. In the Standards, the authors describe the Science as Inquiry content standard in this manner:

Students at all grade levels and in every domain of science should have the opportunity to use scientific inquiry and develop the ability to think and act in ways associated with inquiry, including asking questions, planning and conducting investigations, using appropriate tools and techniques to gather data, thinking critically and logically about relationships between evidence and explanations, constructing and analyzing alternative explanations, and communicating scientific arguments. (p. 105)

Light is particularly suited to students' inquiry. Students already have ideas about light, but the study of light still has surprises for them. From the teacher's point of view, light is cheap and easy to manipulate.

The activities in this lab are organized under two topics: Light in Colorand Laws of Light. For each one, an introduction outlines the rationale for teaching the topic and briefly describes the activities. Follow the links to the activities themselves. There you can access a background page that may include an elaboration of the rationale, grade-level information, and connections to standards for that specific activity. Resources may also be listed to help you investigate the topic further.

Overall, the activities explore sophisticated science without doing a lot of sophisticated data gathering or calculation. All you have to do is think about light—and be ready to have your assumptions challenged.