What is light?

It's a kind of energy called "electromagnetic (EM) radiation" (but this kind of radiation is not harmful, except for an occasional sunburn). There are other kinds of EM radiation too (radio waves, microwaves, x-rays, etc.), but light is the part WE can see, the part that makes the rainbow.

How does light travel?

FAST and STRAIGHT.

How FAST?

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!

How STRAIGHT?

Perfectly straight, until something bends it. The straight paths of light are called LIGHT RAYS.

There are THREE basic ways to control light:

 

1. Block it with something (this makes a shadow)

 

2. Reflect it (change its path with a mirror):

This is called REFLECTION, strangely enough.

 

 

 

 

3. Bend it:

Change its direction by making it pass into another transparent material of different density, like glass or water. This is called REFRACTION, and it's how lenses work.

Another educational site has interactive demonstrations of refraction and reflection (the other site will open in a new browser window).

 

Well, some important, useful, and very cool "things" depend on being able to produce, control, and/or detect light in special ways:

Your eyes

Eyeglasses and contact lenses

Lenses for TV, movie, and photographic cameras

Photocopiers and fax machines

Binoculars and telescopes

Microscope and magnifier

Projectors (overhead, movie, slide, TV)

CD players

Supermarket product code laser scanners

Weather and spy satellites

Medical systems (to look inside the body)

Solar energy systems

...and many more (not to mention a little thing like PLANTS which use light to grow and to make the oxygen we breathe - but engineers don't make plants).