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Why is the Sky Blue but not Violet?

As we know that there are different colors in the world like blue, white, red, yellow, and so on. When we see the sky, a question comes to our mind ‘Why is the sky blue?’ instead of white, red, yellow, or any other color. It is a complicated concept and before understanding this concept, we have to understand some other things. Along with discussing the blue color of the sky, we will also try to get answers to some relevant questions.Why is the sky blue?


Sunlight is the major cause of the blue color of the sky. We see that the color of the sunlight is yellow but it is not the actual colour of sunlight. The actual color of sunlight is white and white light is a combination of seven colors. The seven colors of white light are given below;

1.     Violet

2.     Blue

3.     Indigo

4.     Green

5.     Yellow

6.     Orange

7.     Red

Wavelengths of Different Colours of Light

The wavelengths of these seven colors of light are also different from each other. First, the wavelength of the violet color is 380-450 nanometers. Secondly, the wavelength of the blue color is 450-485 nanometers. Thirdly, the wavelength of the indigo color is 485-500 nanometers. Fourthly, the wavelength of the green color is 500-565 nanometers. Fifthly, the wavelength of the yellow color is 565-590 nanometers. Sixthly, the wavelength of the orange color is 590-625 nanometers. At last, the wavelength of the red color is from 625-740 nanometers.

Scattering Phenomenon

The scattering of the sunlight is becoming the main cause behind the blue color of the sky. According to the Rayleigh scattering formula, the light which has smaller wavelength scatters more. On the other hand, the light which has a larger wavelength scatters less. In the above seven colors of sunlight, the violet color scatters more. After that, the blue color scatters, and so on.

The visible wavelength of the light

The portion of the electromagnetic spectrum that is visible to the human eye is known as the visible spectrum. Electromagnetic radiation in this range of wavelengths is known as visible light. A human eye can see only that light whose range is between 400-740 nanometers.

Why is the Sky Blue?

When the sunlight which is a combination of seven colors (Violet, blue, indigo, green, yellow, orange, and red) enters into the atmosphere of our earth, it is scattered by the gasses and other particles. They are present in the atmosphere of the earth. According to the scattering phenomenon, the violet light scatters more. The scattering wavelength of this light is less than 400 nanometers which is invisible to the human eye. After that, blue light scatters. The wavelength of blue light is 450-485 nanometers. This wavelength of light is easily visible to the human eye. After that, other colors of light are scattered. Due to the scattering dominance of the blue light over the other colors of light, the color of the sky seems blue to us. For a better understanding of this concept, we should learn about the phenomenon behind different colors.

Why is the Sun Yellow?

As we have discussed earlier the actual color of the sun is white instead of yellow. According to the scattering phenomenon, violet, blue, indigo, and green colors of light have smaller wavelengths, therefore, these colors of light are easily scattered. On the other hand, other colors of light like yellow, orange, and red are not easily scattered. That’s why the color of the sun is yellow.

Why is the Sunset Red?

When we see the sun at noon, it appears yellow. On the other hand, when we see it during the sunset, it appears red. During the sunset, the sun is lower in the sky. When it is lower in the sky, its light has to pass through more atmospheres to reach you. As a result, more violet and blue lights scatter. This thing allows the red and yellow lights to pass straight to your eyes. When the light has to pass through more atmospheres to reach you, it will reflect and scatter more red and yellow lights. As a result, the whole western sky starts to glow red.

Is the Sky Blue Due to Ocean?

Most people think that the blue color of the sky is due to the blue color of the ocean. It is a misconception because the blue color of the sky is due to the scattering of the sunlight. Now, another question comes to our mind why the color of the ocean is blue? NOAA (National Oceanic Atmospheric Administration) has provided the answer to this question. According to NOAA, the water can easily absorb shorter and longer wavelengths of light. Therefore, when sunlight hits the ocean, it absorbs its longer wavelengths like red, yellow, green, and orange along with its shorter wavelength like violet. Therefore, there remains only a blue wavelength of light. This blue wavelength of the light is reflected by the ocean. That’s why the ocean seems blue to us.

Why is the Mars Sky Red?

The Viking Mars Landers have sent some photos of Mars’s sky. We can see in these pictures that the color of Mars’s sky is red instead of blue. According to scientists, the red color of the Mars sky is due to the dust storms which occur from time to time on Mars. These dust storms throw iron-rich dust particles into the atmosphere of Mars. These iron-rich dust particles are the main cause of the red color of Mars’s sky. Scientists have also predicted that the color of the Mars sky also changes with the changes in the weather conditions. If there are no storms for lots of time, the color of the sky will be blue.

Is the Sky Blue on All the Planets?

No, the sky is not blue on all the planets. Its reason is that the color of the sky depends upon the atmosphere of a planet. In the atmosphere of the earth, there are gases and other particles. These gases and particles scatter blue light. That’s why we see the blue color of the sky on Earth. Similarly, on Mars, the atmospheric conditions are different from Earth’s atmosphere. That’s why the Martian sky is red. NASA has also sent pictures of the sunset and sunrise on Mars. During the daytime, the Martian sky has an orange or reddish color. On the other hand, during the sunset, it gives a blue-grey tone.

Why Are Clouds White?

As we know that there are some particles of water in the atmosphere of the Earth. These particles of water are bigger than other particles in the atmosphere. When the white light of the sun strikes with these water particles, these water particles scatter all the wavelengths of light in equal amounts. This combination of all the wavelengths of light provides white color to the clouds.

Why are Rain Clouds Dark?

It is a fact that most of the clouds are white but the rain clouds have a darker shade of grey. The water on our earth changes into water vapors due to warmth. These water vapors are less in weight. Due to less weight, they rise. When these water vapors enter into the higher atmosphere of the earth, they have to come across cooler air. The cooler air condenses these water vapors. As a result, they form clouds. No doubt, these water droplets reflect all the colors of sunlight and these are white. Now, the problem is that when lots of water droplets gather, they become thicker and denser. The upper side of these thicker and denser clouds reflects all the colors of light and they don’t allow the light to penetrate through. That’s why the lower side of the rain clouds has a darker shade of grey.

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