Why Does Sky Appears Blue?

Why Does Sky Appears Blue?

As we know that sunlight is mixture of seven colors (VIBGYOR) and each color of white light has corresponding frequency and wavelength associated with it. The violet color has the shortest wavelength of all and red color has largest one. On the other hand earth’s atmosphere is composed of gases, dust particles, water vapors and droplets and among gases nitrogen is present around 78% and is followed by oxygen which is at 21% and remaining 1% composed of other gases like carbon dioxide and argon etc. when sunlight falls on these molecules light get scattered and scattering is the process in which air molecule absorbs sunlight and re-emits it in different directions. The amount of scattering is not equal and it is given by Rayleigh law of scattering. According to Rayleigh criteria of scattering the intensity of scattering light is inversely proportional to fourth power of wavelength. The equation is given by

I α (1 /(W ^4))

From the above equation it can be said that color with shorter wavelength will be scattered more by molecules of air and when light travels to eyes sky appears to blue. 


Wait . . . .

Here the light that should be scattered more is violet but why we see blue color not violet. The answer lies in solar spectrum. When you will see solar spectrum you can clearly see that amount of color violet in solar spectrum is very low and white light (sunlight) contains more amount of blue color that’s why we see blue color of sky. 


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