|If Chlorophyll is a chemical pigment why do plants still reflect green light to make it appear as green instead of the chemical itself?|
|Question Date: 2019-10-17|
When we say that chlorophyll is a chemical pigment, what we mean is that chlorophyll is a chemical molecule that cannot be described as a biological particle like a protein (an example of a biological pigment is the green fluorescent protein, or GFP for short).
Proteins are typically much larger than chemical molecules and have specific building blocks. The chlorophyll molecule actually absorbs red and blue light and reflects green light, and the reason it absorbs certain colors of light and reflect other colors is because of its chemical structure. Many things with colors, such as paints, have colors because they have molecules with rings of carbon atoms.
In fact, the origines of many vibrant colors lies in connected rings of carbon atoms that share their electrons with one another in a large electron cloud around these rings of atoms. Chlorophyll is such a molecule, and its specific arrangement of atoms allows it to absorb red and blue light and reflect green light.
The absorption of blue and red light is useful for plants that have chlorophyll molecules -- plants use the energy from the red and blue light to survive and thrive. Many chlorophyll molecules are needed for plants to survive, so plants appear green.
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Pigments are chemicals that make something appear colorful instead of clear or white. To understand how they work, we have to understand the physics behind colors and light, because without light, there is no color.
White light (coming from the sun) contains all colors within it - remember that the spectrum of visible light is just a small portion of wavelengths that light can travel as, with ultra violet light at the highest energy (shortest wavelength) end and red at the lowest energy (longest wavelength) end:
Generally speaking, all pigments work the same way. White light hits the object, the pigment absorbs a certain portion of the wavelengths, and whatever doesn't get absorbed is reflected back to the viewer. So in plants, chlorophyll absorbs everything but green light - this is why we see the plant as green, because green light is reflected by chlorophyll back to our eyes. You'll notice in the diagram below that carotenoids on the other hand (the pigments present in carrots) absorb everything but yellow, orange, and red light, which is why carrots appear orange.
So really, the answer to your question is that we never see the true 'color' of a pigment, because color isn't really an intrinsic quality of the objects we see. Color is just an artifact of light interacting with molecules in a particular way.
Amount of light absorbed.
I’m not sure that I understand your question, so feel free to write back.
What we see as “white” light is actually made up of different wavelengths that we see as different colors. You can demonstrate that using a prism, or you can look at a rainbow.
When light hits an object, different things can happen. In some cases, it can pass right on through (like the light coming right through your window). If the clear object is dense enough (like thick glass or water), the light is bent as it passes through. It can get scattered as it hits little particles. That’s why light only goes so far down in water. It can also be absorbed or reflected.
When we look at something that’s green--whether it’s chlorophyll or a green book—what hits the retina of our eye is the green wavelengths. That means the green wasn’t absorbed, but the other wavelengths were. The green was reflected back to our eye.
Chlorophyll is a chemical. Everything is made of chemicals. All “stuff” or matter is made of atoms. We can’t see the individual atoms, of course. They’re way too small. But when they get together with other atoms into molecules and then into objects made of countless molecules, we can see them.
To learn more about why different materials reflect different wavelengths, I suggest checking in with our physical scientists.
Why is chlorophyll one of the most important chemicals for life on Earth?
Thanks for asking,
Chlorophyll absorbs the light that isn't green, so the leaves look green because that's the color of light that chlorophyll does NOT absorb.
Chlorophyll absorbs blue and red light
The fact that it is green means that it absorbs blue and red light and reflects green when it is illuminated by white (all wavelengths)
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The color of an non-transparent object is determined by the light it reflects. When light is shined upon an object, the object may absorb some frequencies and reflect the rest. A white object reflects all incoming light and a block object absorb all incoming light.
Chlorophyll absorbs blue and red-orange lights for photosynthesis and reflects green light. Chlorophyll is the reason a leaf appears green. For deciduous plants, those that shed leaves during fall, their leaves stop producing chlorophyll and start breaking down existing ones. This makes other pigments more apparent and turns the leaves yellow.
The leaf itself is mostly transparent, as can be seen in a bleached leaf.
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