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Table of Contents

What Is Light?

Light is a kind of energy called electromagnetic (EM) radiation. This kind of radiation is not harmful, except for an occasional sunburn. There are other kinds of EM radiation too, like radio waves, microwaves, and X-rays. Light is the part we can see — the part that makes the rainbow.

What is light?

How Does Light Travel?

Light only takes 8 minutes

How FAST Does Light Travel?

Light travels about 186,000 miles per second (300,000 kilometers per second), so light from the sun takes about 8 minutes to go 93 million miles (149 million kilometers) to Earth. Does this seem SLOW? Well, if you could drive to the sun at 60 mph (100 kph), it would take you 177 years to get there! In one second, light can go around the Earth 7 times!

Light travels straight

How STRAIGHT Does Light Travel?

Light travels perfectly straight, until something bends it. The straight paths of light are called light rays.

Controlling Light

Child stands in front of fence and creates shadow, demonstrating blocking light

Block It

... with an object or person.

This makes a shadow.

Bird stands in front of two corner mirrors, showing reflections

Reflect It

Change its path with a mirror. This is called a reflection.

See this YouTube demo on light reflection.

Two colored pencils in a glass.

Bend It

Change its direction by making it pass into another transparent material with a different density, like glass or water. This is called refraction, and it’s how lenses work. There are other ways to bend or deflect light, including diffraction gratings and holographic lenses. Scientists have also found that gravity can bend light!

View “Bending Light” demo from the University of Colorado Boulder.

Light Is Produced, Controlled, and Detected in So Many Ways Around You!

Studio camera.

Cameras

Girl wearing black glasses.

Glasses

Children wearing virtual reality goggles.

Augmented or virtual reality

Satellite orbiting earth.

Satellites

Hand holding item scanner..

Scanners

Projector.

Projectors

Person putting contact lens into eye.

Contact lenses

Child looks through telescope.

Telescopes

Field of solar panels.

Solar energy panels

Closeup of microscope.

Microscopes

Surveillance camera in professional setting.

Surveillance cameras

Plants growing under gardening lights in greenhouse.

Gardening lights

Next Topic: What Are Lenses?

Explore
Three young people view futuristic globe icon with light overlay

Continued Learning

Concave vs. Convex Lenses

Most devices that control light have one or more lenses in them. Lenses bend light in useful ways. Learn more about types of lenses and what they do.

What Are Lasers?

Learn about lasers. A laser is a special source of light of only one pure color or wavelength. Find out what is cool about a laser beam.

Resources for Teachers and Parents

Websites, books, curriculum, and resources for teachers and parents on optics.

Scientists and Optical Engineers Use Light

Aren’t scientists and engineers the same thing? Learn what scientists and engineers do, how they’re different, and how you can get involved in these fields.

Introduction to Optical Design

What is optics? What is optical design? Learn how optics connects with optical systems design, optical engineering, lens designs, and camera lens designs.

Notes for Introduction to Optical Design

Expand on your introduction to optical design with additional information on magnifying glasses and lasers, wavefronts and rays, Snell’s law, aberration, and more.

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