Back to Physics






Besides the sun, there are sources providing light:




some animals, such as fireflies and fish such as Sea Sapphires


Lightning and


electric lightbulbs also produce light.




Light exists in two very different forms at the same time.

One form is tiny particles called photons.

The other form is waves.   


Showing light as both a wave and a particle at the same time.



The easiest way to think about light is as waves.

Light waves travel through space at a speed of about

The color of light depends on its wavelength.

Red light has the longest wavelength.

Violet light has the shortest wavelength.

Orange, yellow, green, blue, and indigo have wavelengths in between those of red and violet.

When light waves of all the colors travel together, the light looks white.


When light travels through a prism, waves of different wavelengths bend by different amounts.

The color of each wavelength then appears separately.

This effect is called a spectrum.

A rainbow is a type of spectrum.

Light is very important to life on Earth.

Using the energy of light, plants combine a gas in the air called carbon dioxide with water in the soil.

Through this process, called photosynthesis, plants make their own food.

People and other animals then use plants for food.

As plants make food, they also give off a gas called oxygen.

People and other animals need oxygen to stay alive.