Chlorophylls reaction to the visible spectrum
Introduction/aim: To investigate the effect of chlorophyll on visible light in a
Question/hypothesis If the solution of chlorophyll is put in a beam of light then the
green will disappear from the spectrum.
theory: To be able to understand the concept of
chlorophylls reaction to the visible light, we have to learn about
photosynthesis and light. Starting we have Photosynthesis
which is a process plants use to turn light energy into sugar (glucose) to be
able to gain energy (nutrition) for themselves. The plants (autotrophic such as
algae) contain pigments found in the chloroplast of the cell plants. In the
chloroplast there is a pigment called chlorophyll (plants have two types,
chlorophyll a and b). The chlorophyll only absorbs the red and blue light
(light waves) which becomes a reflection of green and therefore gives the
plants a green reflection. The light that the plants absorb travels in waves, a
form of electromagnetic radiation. The focus for now is to learn about the
visible spectrum, which is “the only part of the electromagnetic spectrum that
can be seen by the human eye” (Khan Academy, 2014). When the sun shines on
plants, we see the light as white but in fact, it consists of different colors,
which we can see through a prism. When the white light shines on a prism, the
wavelength of light bends into different angles that spread out, and therefor
turns into the colors of the rainbow, all colors visible by the human eye. (Khan
– Beaker (small)
– Beaker (big)
– Heat pan/hot plate
– Visible light beam
– Filter paper
– Plastic rap
Start with boiling water on a
heat pan, add your leave, and let it be in the water for 1 minute.
Take out the leave from the
water and cut the leave into small pieces.
Put the small leave pieces into
the mortar and start molting the leaf with a bit of sand.
Add some acetone to the sand
leaf mixture and keep on molting until you are left with a dark green mixture.
Now that you have the dark
green mixture, filter the solution using a filter paper and a funnel and pour
the filtered solution into a beaker.
Add the plastic wrap on to the
beaker filled with the filtered green solution
Turn on the visible light and
shine it on the whiteboard.
Use the prism to break the
visible light into the different parts of light that white light has.
Hold the chlorophyll between
the light and the prism.
Observe the results and write
The colors in the visible turned green due
to the chlorophyll solutions reflection. This happened when the solution was
placed in front of the prism and visible light was shined onto the prism
(picture shown above)
In my hypothesis, I wrote that I think that
if the solution of chlorophyll is put in a beam of light then the green will
disappear from the spectrum, which was wrong. The correct hypothesis would be
that if the solution of chlorophyll is put in a beam of light then the green
will out shine all the colors from the spectrum turning them all into the same
color as the chlorophyll solution, which is green. This means that my
hypothesis was incorrect, in other words it was refuted since the green color
did not disappear, instead all other colors turned green.
When looking back at the background
theory, we learn that plant chlorophyll consists of both chlorophyll a and b
which absorb the red and blue light (light waves). The green light waves are
not absorbed but reflected instead which gives plants their green appearance.
This makes it obvious that the color of the solution, which was green, will be
the reflection showed on the whiteboard when held in front of a prism because
the red and blue are absorbed and not shown back. We use a prism to be able to
see all the colors individually but since the leaf absorbs the red and blue
colors, the only reflection will be the green wavelengths. So even though the
prism is separating for you, only the green is really getting reflected and
shown. The color that the human eye sees in plants is mostly due to which
colors are absorbed by the plant and which ones are reflected.
Some errors that could occur while
preceding this experiment could be that you didn’t mold the leaf enough
resulting in a light green liquid instead of a dark strong color of green. This
would lead to a failure when putting the liquid in front of the prism since the
color would be to weak to out shine the rest of the colors. This is something
that happened to a group resulting in not all visible colors becoming green,
only some that isn’t correct. Therefore, you have to be sure to mold the leaf
mixture until you have a dark green liquid.
Another error could be the measurement of
each ingredient. On the description, it said that you should add a pinch of
salt and a small amount of acetone which if you use to less or too much of
could ruin the result. If you use too much sand the mixture could become too
thick which could make the solution grumbly and give you inaccurate results
when the light shining onto the prism hits the solution. If you have too much
acetone, the liquid can become to liquidly and give a light green color even
though you molded the leaf as much as possible which also would give you an
inaccurate result. Therefore, you have to be careful when adding ingredients to
A way to improve the results in this experiment according
could be to try the same experiment with a prism but with different plants that
consist of other colors such as a pink flower or a yellow dead leaf. In that
way, you would change the variable since these plants consist of other pigments
such as yellow and red and then see how their reflection would be shown in
front of the prism. Then you could compare and see if they also outshine the
other colors like the green did or if the green color is a stronger one and how
different pigments are stronger than others are.
Khan Academy, 2014.
– Own knowledge from Ms Galleys lessons