A great question! Lots of things happen really,
but I will talk about two effects that are pretty
The first is heating things up and the
second is the discoloration of things left
out in the sun for too long (e.g., if you've ever
left out drawings or crafts like I have).
We will see that both originate from two different
effects of the same thing:
First, a little physics.
Light, as you will learn in physics class,
is a form of energy.
It is useful in this context to think of light
as wave, with some frequency (how wiggly it is)
and amplitude (how big the wiggles are).
We learned in the early 1900s that as the
frequency of light increases, so does the energy
it carries. It turns out, light can exist on
many, many frequencies that span what is known as the
The inverse of the frequency is the
wavelength, so small frequency equals large
wavelength. Only a small part of the
electromagnetic spectrum is visible to the human
eye. We recognize this as color.
However, there are many, many wavelengths (aka
frequencies) of light that range from the
length of an athletic field to that of an atom.
Light from the sun
spans a pretty large chunk of the electromagnetic
You'll notice a small part is called UV
(this is the part of the spectrum sun screen
protects against). A sizeable chunk is in the
visible (that what let's us see things in the
day), and a huge portion is in the infrared.
Infrared is essentially energy in the form of
heat, which is why things get warmer under the
Things discolor mainly because of the UV.
UV light is high in energy, so it is able
to cause chemical reactions that leads to changes
There are of course a whole host of things that
can happen when sunlight hits an object that is
entirely dependent on the properties of that
In fact, optimizing the amount of light that is
absorbed is a key materials science challenge
for solar cells! Nevertheless, it all comes
down to the electromagnetic spectrum of the
Hope this helps!