The sun is our major source of light and heat for our planet. It spreads a variety of distinct colors across the sky every day. It is fascinating to see the sky change its hues from light red to bright golden shimmer and then to a pink glow during the sunset. Just by looking at the sunlight, one often thinks that sunlight is yellow and then, it gradually changes to orange. However, upon closer scientific inspection, the facts point to something else entirely – that sunlight is actually white in color. But on deeper inspection, the white light of the sun is divided further into seven colors of the rainbow. So, let us understand what color sunlight exactly is and why it is so.
The Colors Present in Sunlight
Let us visualize the colors present in sunlight with the help of a simple experiment:
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Take a glass prism and set it up in a dark room near the window such that direct sunlight falls on the prism through a small aperture in the window.
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Fix a whiteboard to capture the rays passing out of the prism.
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The observation shows that the whiteboard has a spectrum of seven distinct colors, which are the colors of the rainbow, i.e., violet, indigo, blue, green, yellow, orange, and red.
Thus, we can conclude that the white light of the sun’s rays is actually made of a combination of seven constituent colors.
Why are there 7 Colors in Sunlight?
The sun’s rays are actually white in color and form a mixture of the seven colors we see in a rainbow, i.e., Violet, Indigo, Blue, Green, Yellow, Orange, and Red, commonly called VIBGYOR. The sun appears to have different colors during the course of a day because of a process called dispersion. Dispersion of light is a phenomenon by which white light splits up into its seven constituent colors, due to the refractive index of the surface of incidence, and the different speeds the different constituent colors have in a medium. The refractive index of a material is defined as a dimensionless number that can describe how fast light travels through a particular material. Different lights have different wavelengths, and hence, different refractive indices in a given material. This causes them to split apart from the original white light, and form a spectrum of the seven colors.
The Different Colors of the Sun at Different Times in the Day
The earth’s atmosphere is made up of various different gasses like oxygen, nitrogen, and carbon dioxide. In addition, there are other impurities like dust, smoke particles, and polluting gasses like methane and CFCs. When the sun’s rays strike the earth’s atmosphere to pass through, they are distorted by the earth’s atmosphere due to the presence of all these materials in the atmosphere. As demonstrated earlier, different colors present in the spectrum have different wavelengths.
The wavelength of a material can be defined as the distance between two successive crests(highs) or two successive troughs(lows) of a wave. So, the longer the wavelength, the lower the frequency. Thus, blue and violet are scattered more because of their short wavelengths. Conversely, colors of the other end of the spectrum do not get scattered as much, because they have longer wavelengths. Thus, there are different colors of the sun at sunrise and sunset.
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When the sun is directly over us during late morning and noon, the sun’s rays are subject to the least amount of interference because the distance traversed by the rays is the least at that time. Therefore, during this period, blue light gets scattered, and the sky appears to be blue, while the sun’s rays appear to be yellow.
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During sunrise, the sun is at its farthest, seemingly rising from the horizon. As a result of this, the light rays have to travel a much longer distance through the atmosphere. Therefore, they are obviously subject to more interference, resulting in an increased amount of scattering. Consequently, out of all the colors, the red light is least scattered. The same phenomenon occurs during sunset when the sun is seemingly moving towards the horizon, and as a result, the sunlight color appears to be of varying shades of red and orange during the dawn and dusk.
Sunlight
Sunlight can be defined as the energy and light which comes from the Sun. It is called insolation when the sun’s energy reaches the earth’ surface. What the dwellers of the earth experience are the solar radiation of the sunlight. The heat and radiation from the Sunlight come in the form of electromagnetic waves. When the solar radiation enters the earth, then the atmosphere absorbs about 16% of the solar radiation and some 6% is scattered to space. 28% of the solar radiation is reflected by the clouds and about 47% reaches the earth’s surface. Without the presence of sunlight, no life could survive on the planet. The plants require sunlight for making food by the process of photosynthesis. Here, the plants use solar energy, water and carbon dioxide to form carbohydrates and oxygen. Thus, without sunlight, no life will be able to survive on earth. Solar energy can be both beneficial and harmful for us. The human body requires sunlight for the synthesis of vitamin D in their body. But if there is an excess of sunlight then the radiation can lead to sunburn and skin cancers.