Ask Dr Stupid: Subject: ltjexg gdzi
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Message: why is the sky blue ?
why is the grass green not purple?
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Why is the sky blue? This is a relatively simple answer. Sunlight is made up of many different colors. The colors in the longer wavelengths are more in the reds, while teh shorter wavelengths are in the blues and purples This is easily seen in raimbows, with the reds on the outside and the blues and purples on hte inside. Similarly, sunlight entering our atmosphere hitting air particles, which causes the light to scatter and diffuse. This scattering is done mainly to the shorter wavelength colors, so this happens more in the blues and purples. As our eyes are more sensitive to blues than purples, this give us the appearance of the sky being blue. IF you are seeing other colors, then you are wearing color glasses or other wise looking through some sort of color filter, are color blind or on drugs.
Why is the grass green and not purple? Again, we look to the sun for the answer. For the most part, plants are green. This is because plants contain chlorophyl, which is a green substance that is in many of the plants cells, especially the leaves. Chlorophyl is an essential ingredient in photosynthesis, in which the plant uses nutrients obtained from their environment combined with sunlight to convert into simple sugars that the plant in turn can use as food and energy. But, this doesn't answer your question. The reason grass is green also because of the same chlorophyl that has just been prevoiously mentioned.
But what is color? Color is really the reflection of specific wavelenths of light, or in some cases, light not absorbed. As a result, due to the chemical composition of most grasses, the leaves simply reflect the color green, which we then perceive as the colors we call green. But not all grasses are green. Kentucky Bluegrass is more of a blue-green, for example. Other grasses exhibit other colors. Yellow and brown are common colors seen from grass, especially dead or dying grass. This is because the chlorophyl has become depleted, and so the grass now reflects different colors that were hidden because of the presence of chlorophorm.
A more dramatic example of how chlorophorm plays a factor in plant coloring is in trees, especially in certain parts of the country. During the months of autumn, many trees lose their leaves. Before the leaves fall of the trees, many people observe the leaves "turning colors". This is not actually true. What is happening is that the chlorophorm is exiting the leaves or dying as the tree cuts off circulation to the leaves. With the chlorophorm gone, the "natural" color of the leaves is shown. These colors can be in a wide range of colors, even in a single tree. It is not unusual to see not only expected colors such as browns and yellows, but also gold, red, orange and other similar types of colors. Like with the grass, the tree leaves are no longer reflecting the green from the chlorophorm, but the left behind colors of the dead leaves.
So, the reason why grass isn't purple is because the dominant chemical in the plant is green, not purple. Perhaps you'd like to genetically engineer purple grass?
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