Good question. Believe it or not, the light
that seems colorless actually has all the colors
of the rainbow in it. What’s my
We call sunlight and other “colorless” light
white light. Each color of light is made by
tiny packets of light called photons
travelling at a different wavelength. Here’s a
picture of how different wavelengths are different
When we see all the wavelengths together, we don’t
see any color. But if we shine that white light
through a prism the white light is split into all
the colors of the rainbow. The web site above
You can do this yourself if your teacher has a
prism. You may even have glass around your
house that makes a rainbow on the wall. We see
rainbows in the sky when the light shines through
water droplets in the sky at the right angle.
When the white light hits an object, some
wavelengths get absorbed. The light energy is
usually given off as heat, but pigments like
chlorophyll trap the light energy and use it to do
the work of making sugar from carbon dioxide and
Wavelengths that are not absorbed get
reflected. Those are the ones that hit your
eye. So if something looks green, which
wavelengths are being absorbed and which are being
reflected? Here’s a challenge question:
Which wavelengths of light is a plant actually
using to get its energy?
You may be interested in studying the way light
behaves in physics or how plants use light in
Thanks for asking,
When we see an object of a certain color, it is
because the object absorbs light of all colors
except for that color, which we see. So, for
instance, if we see someone wearing a red
shirt, that shirt looks red because it reflects
red light, while it absorbs other colors of
Chlorophyll is a pigment that absorbs mostly
red and blue light and reflects mostly green
light, so it appears green to us.
So what does it mean to "absorb" light?
Light has wavelike properties, which means it can
exist with different wavelengths. Each
different wavelength of light corresponds to
different energies. Some of those wavelengths
correspond to types of light we can see (colored
light). Other wavelengths correspond to types of
light we can feel (for example infrared, or heat),
and others still we cannot see or feel directly
but can do damage to our cells (e.g. UV, X-Ray).
The collection of wavelengths at which light can
possibly exist is called the electromagnetic
Visible light -- the range of wavelengths
that allows us to see all the colors and objects
we can -- actually only comprises a very small
portion of the electromagnetic spectrum!
Furthermore, each different wavelength or type
of light has a different amount of energy
associated with it. When light hits matter, which
is comprised of molecules, the molecules in the
object can either absorb, reflect, transmit, or
scatter the light. Usually some combination of
these phenomena occurs, because the kind of light
hitting the object usually comes with some range
of wavelengths/energies. When light from the
sun hits chlorophyll molecules, the red and blue
wavelengths excite the electrons in the
chlorophyll (i.e. get absorbed) -- that's what
drives photosynthesis! The green
wavelengths in the sunlight, on the other
hand, get scattered and reflected, so we
see plant leaves as green!
What is called 'white' light is actually a mixture
of radiation of different wavelengths. These
wavelength each have their own cold: from RED to
BLUE. Now, Sunlight is a mixture of all these
colors and looks “white”. When sunlight falls
on a plant, the chemicals in the planet cells
ABSORB most of the wavelengths but REFLECT
Green. That is the green light which is NOT
absorbed but instead is reflected. Plants look
green because the reflected light is predominantly
composed of radiation of the wavelength that
corresponds to GREEN light.
Great question! This story begins with
understanding what light is. Unfiltered sunlight
arrives on earth in all wavelengths of the visible
spectrum (the whole rainbow, purple to red).
Plants can only use certain wavelengths of light
and reflect all other wavelengths. Chlorophyll
absorbs particular wavelengths but reflects green.
This reflection of green from plants gives them
their green color! This is why when leaves are
dying and chlorophyll is breaking down, they
change colors (yellow, red, brown)!
Click Here to return to the search form.