Introduction

Light is everywhere in our world. We need it to see. It carries information from the world to our eyes and brains. 

Light is a form of energy.  Light energy can be changed into heat, electricity and other forms of energy.  Light travels in a straight line and can't  go around corners.  The fastest possible speed anything can have is the speed of light.  Nothing can travel faster.  Light travels 186,000 miles a second.  It takes less than two seconds for light to reach us from the moon.  The distance that light travels in one year is called a light year.  The nearest star is 4.2 light-years away.

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 travels in waves.  There are four properties of light waves: speed, wave-length, frequency, and amplitude.  Light waves are like water waves.  The top of each wave is called the rest.  The distance from the crest of one wave is called wave-length.  You already know the speed of light - the fastest possible speed.  The number of waves that pass by each second is the frequency of the wave. The height of the wave is amplitude.  Waves of light travel out from a lamp to all parts of the room.  Wherever the waves are moving, they are moving in a straight line. 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.
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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  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.

Read more about light.

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