What happens when the sunlight travels through the Earth’s atmosphere?

Question

Question

This question was previously asked in

NDA-I (GAT) Official Paper (Held On: 13 Apr, 2025)

Answer 1

CONCEPT:

Scattering of light: The phenomenon in which the light ray is redirected in all other directions on passing through particles of dimensions comparable to the wavelength of the light used is called scattering of light.
Rayleigh scattering: The scattering of light off of the molecules of the air that can be extended to scattering from particles up to about a tenth of the wavelength of the light used is called Rayleigh scattering.

According to Rayleigh scattering:

Scattering \(\propto \frac{1}{{{\lambda ^4}}}\)

Where λ is the wavelength of light

For white light:

Order of wavelength:

Violet < Indigo < Blue < Green < Yellow < Orange < Red

EXPLANATION:

According to the above, the scattering is inversely proportional to the fourth power of the wavelength of the light.
As we know that in primary colour (blue, green, yellow, orange and red), the blue colour is having least wavelength and therefore scattered the most.
The scattered light is the sky contains abundant blue light and therefore sky appears blue. So option 1 is correct.