Why is the sky blue ? Why is the ocean blue? Why does it seem like blue is the nature's favourite colour?

Some people think the sky in blue because of sunlight reflected off the ocean and back into the sky. But the sky is blue even in the middle of the country side nowhere near the sea!
Other's think it's because of the water in our atmosphere. But the sky is blue in the places that are extremely dry like desert.
Some say it's because of oxygen is blue coloured gas. Or because sunlight has a blue tint.

So there are so many incorrect answers or you can say misconceptions are there--

What's the actual reason?

The sky is blue because of the way sunlight interact with our atmosphere.

1. Sunlight is made out of light of different colours/ wavelengths.

2. The Earth's atmosphere is made out of molecules that scatter different wavelengths light.

3. The sensitivity of our eyes.

If sunlight passes through a transparent material such as water ,glass then the light rays refract , because we know that light changes its speed when it's travel from one medium (air) to another (water) medium.
Similarly prism break up White light into different colours, because these colours have different wavelengths as well as their speed , as they pass through the prism.
The fact that light of different wavelengths respond differently.
There is a scattering phenomenon, which is called Rayleigh scattering, which refers to the selective scattering of light.

Rayleigh scattering is heavily depends on the wavelength of light, so if the wavelength of light is shorter than it will more scatter.
Do you remember the rainbow?, which appear in rainy season, and it's the result of scattering of light and when sunlight enters into the moisture i.e. water molecule, that is already present in atmosphere and these water molecules or droplets behave like a prism and scatter the sunlight into 7 colours, which are said to be VIBGYOR.

At one end of the spectrum is red light , which has the longest wavelength and at the other end is blue and violet light which have a much shorter wavelength.
When sunlight reaches the Earth's atmosphere it is scattered , or deflected by tiny molecules of gases (mostly N2 and O2) in the air.
Because these gases molecules are much smaller than the visible light.
As we have discussed before, shorter wavelength (blue and violet) scattered more strongly than the longer wavelength (red).
But the wavelength of violet is much shorter than blue , then the sky should have appeared violet but it's blue.
Because our eyes are much more sensitive towards blue colour and because some of the violet light is absorbed in the upper atmosphere.
When the Sun is high in the sky, it appears white.

This scatter the blue and green light along the way, allowing the redder light to pass through.
This is because the light from the horizon has had further to transfer through the air and so has been scattered and re- scattered.

Because red , orange, yellow (longer wavelength) light are absorbed more strongly by water than the blue (shorter wavelength), it is mostly the blue that gets return.
"Same reason the sky is blue " , but it works only when the water is clear/ very pure.
If any impurity is present like if water is full of mud, algae, the light scattered off these impurities will overwhelmed the water's natural blueness.

Why milk appear white in colour?

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