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Sign up! Category: Space Published: July 3, The color of the sun is white. The sun emits all colors of the rainbow more or less evenly and in physics, we call this combination "white". That is why we can see so many different colors in the natural world under the illumination of sunlight. If sunlight were purely green, then everything outside would look green or dark. We can see the redness of a rose and the blueness of a butterfly's wing under sunlight because sunlight contains red and blue light.
The same goes for all other colors. When a light bulb engineer designs a bulb that is supposed to mimic the sun, and therefore provide natural illumination, he designs a white bulb, not a yellow bulb. The fact that you see all the fundamental colors present in a rainbow which is sunlight split by mist and no colors are missing is direct evidence that sunlight is white.
The sun emits all colors of visible light, and in fact emits all frequencies of electromagnetic waves except gamma rays. This includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, and X-rays. The sun emits all these colors because it is a thermal body and emits light through the process of thermal radiation.
However, the energy contained in ultraviolet rays is higher, so instead of just causing the molecules to shake, it actually can knock electrons away from the atoms, or causes molecules to split. This results in a change in the chemical structure of the molecule. This change is especially detrimental to living organisms, as it can cause cell damage and deformities by actually mutating its genetic code. This is simply a convenient way of classifying the rays based on the amount of energy they contain and their effects on biological matter.
Luckily,UV-C rays do not reach the earth's surface because of the ozone layer. When UV-C rays meet the ozone molecules at high layers of the atmosphere, the energy inherent in them is enough to break apart the bond of the molecule and absorb the energy. Therefore, no UV-C rays from the sun ever come into contact with life on earth, though man-produced UV-C rays can be a hazard in certain professions, such as welders.
As their energy is often not sufficient to split an ozone molecule, some of them extend down to the earth's surface. UV-A rays do not have enough energy to break apart the bonds of the ozone, so UV-A radiation passes the earth's atmosphere almost unfiltered.
This can be done through a variety of ways. The most obvious is to reduce the amount of time one spends in the sun, particularly between the hours of 11 am and 3 pm, when the sun is at its highest in the sky. However, especially during the summer holidays, this does not always work out.
More ways to protect ourselves can be found here. UV levels are not constant over the course of a day, or even over the course of a year. An obvious factor is the position of the sun in the sky. At noon, for example, the electromagnetic waves emitted from the sun travel a much shorter path through the earth's atmosphere then they would at, say, 5 pm, and thus noon-time intensity is stronger. A second important parameter determining UV at the ground is the amount of ozone present in the stratosphere.
Low ozone correlates with much UV. However, there are many other features of the environment that contribute to UV radiation variability. Most important are clouds. On cloudy days, UV levels are usually lower than during clear skies as clouds can deflect rays up into space. Clouds can, however, also lead to increased UV levels.
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