By Sean W. Henry
Table of Contents
Chapter One
Nature’s Beauty����������������������� 1
Chapter Two
Sir Isaac Newton ������������������� 2
Chapter Three
Making a Rainbow����������������� 3
Chapter Four
Colors in Order
��������������������� 4
Chapter Five
Double Rainbows ������������������� 5
Chapter Six
Rainless Rainbows����������������� 6
Glossary����������������������������������� 7
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Chapter One
Nature’s Beauty
W
hen you look up in the sky after a rain,
what do you sometimes see? One of nature’s
most beautiful sights, a rainbow! If you have
ever wondered what makes a rainbow, you are
not alone. Throughout the ages, people have
wondered about rainbows. They have created
many myths to explain what a rainbow is.
Different peoples have thought of the rainbow
as a bridge to magical lands or a path to
hidden treasures. Today we know the science
behind rainbows.
Because light from the sun appears to have no
color, it is called white light. However, white
light is not really colorless. It is made up of
many colors: red, orange, yellow, green, blue,
indigo, and violet. These colors are known as
the spectrum. When you see a rainbow, you
see white light that has been split into its
different colors.
Title: Over the Rainbow
Grade: 4
Page: 1
Beam of light
Prism
red
orange
yellow
green
blue
indigo
violet
Chapter Two
Sir Isaac Newton
S
ir Isaac Newton was an English scientist. He discovered gravity
by accident! One day he saw an apple fall from a tree. He began to
wonder why things fall down. From this event, Newton developed his
theory of gravity.
In 1666, Newton also discovered something about light. He
experimented with a prism. A prism is a multiple-sided piece of glass.
Newton found that when white light passed through a prism, it split
into multiple colors.
When light moves from one material to another, it bends. For example,
when light travels from air to glass, it bends. This bending is called
refraction. When white light is refracted, it splits into the spectrum.
Title: Over the Rainbow
Grade: 4
Page: 2
Chapter Three
Making a Rainbow
W
hat does Isaac Newton’s work with prisms have to do with
rainbows? Everything!
When the sun shines on raindrops in the air, those raindrops act like
tiny prisms. Sunlight hits the raindrops and bends. The white light
splits into the colors of the spectrum. Some light passes through the
raindrop. However, the rest of the light reflects off the other side of
the raindrop. It is refracted again as it leaves the raindrop.
That light is what you see in the rainbow.
Light refracts
Light reflects
White light
from the sun
Some light
passes through
Light refracts
Where Is the Sun?
You see a rainbow when there is rain, but the sun must be shining,
too! The sun’s rays come from behind you and hit the raindrops. Then
they are refracted and reflected back to your eyes. This creates the
rainbow of color you see.
Title: Over the Rainbow
Grade: 4
Page: 3
Drop A
White light
from the sun
red
orange
yellow
green
Drop B
blue
indigo
violet
Chapter Four
Colors in Order
Y
ou may have noticed that rainbows are red at the top and violet
at the bottom. Do you know why the colors are always in the same
order? It has to do with how the light reaches your eyes.
When light bounces off raindrops at the top of the rainbow, you see
only red. Only red light is refracted at the correct angle for your eyes
to see. The other colors bounce off at lower angles, so your eyes don’t
see them. Raindrops just below the red area also reflect all the colors.
However, only the orange light is at the correct angle for your eyes to
see. Next comes yellow light. Below that are green, blue, and indigo.
Violet light bounces off the raindrops closest to the ground.
Title: Over the Rainbow
Grade: 4
Page: 4
Chapter Five
Double Rainbows
W
hat can be more beautiful than a rainbow? A double rainbow!
How does this happen? When sunlight enters a raindrop, not all of the
light escapes after being reflected once. Some of the light is reflected
again, leaving the raindrop at a different angle.
The first rainbow of a double rainbow is called the primary rainbow.
It is created from the light that is reflected once. The secondary
rainbow is created from the light that is reflected twice.
Title: Over the Rainbow
Grade: 4
Page: 5
Chapter Six
Rainless Rainbows
D
id you know you can see rainbows
without rain? Some things refract light
like raindrops do. As light moves over
their surfaces, the colors change. This
is called iridescence, a play of colors
that resembles a rainbow. Oil slicks
and soap bubbles can create rainbowlike effects. Some beetles look like
they are made of colorful foil that
changes color in the light. Fish scales
and some birds’ feathers can look like
this, too.
The word iridescence comes from iris,
the Greek word for rainbow. According
to Greek mythology, Iris was also
the Greek goddess who personified
the rainbow. She carried messages
between the gods and the humans.
The iris flower was named after this
goddess because irises come in many
colors. Also, the colored part of your
eye is called iris.
People have always loved rainbows.
Even when you know the science
behind rainbows, they still have the
power to thrill.
Title: Over the Rainbow
Grade: 4
Page: 6
Glossary
develop:
(verb) to create or construct.
gravity: (noun) force by which all objects in the universe are pulled
towards each other.
iridescence: (noun) mix of colors that looks like a rainbow.
myth: (noun) made-up story that explains something in nature.
primary:
(adjective) most basic; first one.
prism: (noun) transparent object with multiple sides that refracts and
separates white light into colors.
refraction: (noun) bending of light.
secondary:
(adjective) of lesser importance or value; not first.
spectrum:
(noun) colors of the rainbow: red, orange, yellow, green,
blue, indigo, and violet.
theory:
(noun) idea that explains why or how something happens.
Cover: Jure Porenta/iStockphoto; Page 1: Gwoeii/shutterstock; Page 2 through 4: Steve Stankiewics; Thinkstock/Jupiterimages;
Page 5: Kotenko Oleksandr/shutterstock; Page 6: Kasza/shutterstock; Cosmin Manci/shutterstock; Cosmin Manci/shutterstock
Title: Over the Rainbow
Grade: 4
Page: 7