jueves, 22 de julio de 2021

Why is the sky blue?,

 To answer this question, let's start by talking about sunlight. Sunlight is made up of all the colors of the rainbow, so when we see white light, we are actually seeing light of all colors at the same time.


How is sunlight, rainbows, and longitudinal waves related to the color of the sky? At the EAFIT Children's University we tell you about it.

They ask:  Manuela Bedoya, 12 years old, Natalia Hoyos, 10 years old, Isabela Botero, 7 years old, Juan José Escobar, 10 years old.

Answer:  Nicolás Guarín, physical engineer.

To answer this question, let's start by talking about sunlight. Sunlight is made up of all the colors of the rainbow, so when we see white light, we are actually seeing light of all colors at the same time. In addition, the light behaves like a wave, that is, what is traveling with the light are vibrations that are very fast.

The different colors of light are actually waves with different lengths. As can be seen in the drawing, red light has a greater length than orange light and blue light. Light travels in a straight line and since the Sun is very far from the Earth we can assume that the rays of light that reach us from it are parallel.


There are small particles in the Earth's atmosphere. When sunlight hits the ground, these particles cause light of some colors to be deflected and light of other colors to follow its course (as seen in the drawing). Then the light that has a greater length (red, orange, yellow and green) travels without being disturbed, while the light of less length (blue, indigo and violet) changes its course when meeting these particles.


The phenomenon by which the change of direction of light occurs is known as scattering. But light of shorter length doesn't just change its course upon reaching the atmosphere. nce it keeps changing its course and spreading to the encounter more and more particles. Finally, what we perceive is that blue light comes to us from many particles, because it has been scattered by many of them in the Earth's atmosphere (see figure).


Since the longest light is not so affected by particles in the atmosphere, it reaches us directly from the Sun. Therefore, green, yellow, orange and red light rays arrive without being scattered in the atmosphere. The sum of the green, yellow, orange and red light is what makes us perceive the solo as if it were yellow. Then the phenomenon of light scattering in the atmosphere is causing not only to see the sky blue but also that the sun has a yellow color for us.

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