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KOMPAS.com– Sky biru always considered to imply that the weather is sunny and sunlight very hot.
Before understanding why the sky is blue, it is important to know the nature of sunlight and how it interacts with the gases in the Earth’s atmosphere.
Anthony D. Del Genio of NASA’s Goddard Institute for Space Studies and Columbia University, as quoted from Scientific American, Friday (16/10/2020) explained that in our eyes, the sunlight will appear white.
In fact, it is actually a mixture of all the colors of the rainbow.
Sunlight passing through the atmosphere in air molecules up and down, it is caused by electromagnetic waves that cause the particles to be charged with electrons and protons.
Also read: The Secret of the Universe: Why Are the Stars Flickering in the Night Sky?
When this happens, the oscillatory charge will produce electromagnetic radiation at the same frequency as the incoming sunlight, but spread out in all different directions. This diversion of incoming sunlight by air molecules is called scattering.
From light spectrum, the blue component has a shorter wavelength and a higher frequency than the red component.
Thus, when sunlight from all of the color spectrum passes through the air, the blue component causes charged particles to oscillate faster than the red color.
The faster the oscillation, the more scattered light is produced, so blue is stronger than red.
Also read: Are the skies on other planets as blue as the earth?
There are quite dramatic differences for particles such as air molecules which are much smaller than the wavelength of visible light.
The acceleration of a charged particle is proportional to the square of the frequency, and the intensity of the scattered light is proportional to the square of this acceleration. Therefore, the intensity of the scattered light is proportional to the strength of its frequency.
The result is that blue light spreads in the other direction almost 10 times more efficiently than red light.
When the eye sees any point in the sky, away from the sun, it will only see light that has been diverted by the atmosphere into our line of sight.
The purple light was actually scattered even slightly stronger than the blue. However, our eyes are more sensitive to blue light than purple, so the sky appears blue.
It’s different when we see the sun setting on the horizon. Our eyes only see light that has not yet been scattered in another direction, at which time the red wavelength of sunlight that has not been scattered through the air reaches the eye.
More opportunities for blue light to scatter than when the sun is overhead. The greater distance that the sun’s rays travel through the atmosphere while on the horizon amplifies the effect, thus, the setting sun appears reddish.
Clouds, on the other hand, are made of water droplets that are much larger than the wavelength of visible light.
Also read: The Secret of the Universe: Why Are the Sea and Sky Blue?
The way they scatter sunlight is determined by how the light is internally refracted and reflected by diffraction around, cloud droplets.
For these particles, the difference between the scattering of blue and red light is not as great as for the gas molecules.
Therefore, our eyes receive substantial diffused light at all visible wavelengths, causing clouds to appear whiter than blue, especially when viewed against a background. blue sky.
Because scattering by the atmosphere causes the sky to turn blue, a planet without an atmosphere cannot have a clear sky.
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