Question

The sky looks blue due to-
(A) Dispersion effect
(B) Reflection
(C) Transmitting
(D) Scattering

Answer 1

Hint:The light of shorter wavelength will have less tendency to travel more, hence the light of shorter wavelength will travel less and this is the reason that the light of shorter wavelength will scatter more and the light of larger wavelength will scatter less in comparison of the light of the shorter wavelength. Hence wavelength is the key factor to get the solution of the above given problem.

Complete step by step solution:
> When the light passes through the atmosphere then it is subjected to the different types of molecules of the air and gases in the atmosphere. As we all know that the air is a colloidal mixture of the solid sol and the colloidal solution will make the light scatter when the light passes through it. The molecules of air make the light to be scattered. Since the lights are made up of seven different colours and those seven colours have different wavelengths.
> Light has its visible range in between the IR and UV spectrum that are composed of the following lights of different colours, and the wavelength.

S.N.	Lights of the different colours	Wavelengths
	Red	\[{\text{(625 - 740)nm}}\]
	Orange	\[{\text{(590 - 625)nm}}\]
	Yellow	\[{\text{(565 - 590)nm}}\]
	Green	\[{\text{(520 - 565)nm}}\]
	Blue	\[{\text{(445 - 520)nm}}\]
	Indigo	\[{\text{(425 - 445)nm}}\]
	Violet	\[{\text{(380 - 425)nm}}\]

We know that the light of less wavelength is scattered more than that of the larger wavelength. Here we see that the Blue light has shorter wavelength than the red light, orange light ,yellow light and green light, that’s why it is scattered more than the lights of the comparatively larger wavelengths ( Also the other two colours of lights are similar to the blue so their scattered beam also appears to be blue). This is the reason because of which blue light is scattered more than the other light of other colour by the molecules of air. Due to the scattering of blue light, the blue colour spreads all over the sky and other colours travel more into the sky than the blue colour and that’s why the sky looks blue.> The sky looks blue due to the scattering of light.So, the option (D) is the correct answer.

Note:Sometimes there is a misconception that the blue colour of the sky is because of the blue colour of the ocean but now we have a clear concept that blue colour of the sky is due to the scattering of the light by the molecules of the air and gases and same concept is applied for the blue colour of the ocean. Hence the blue colour of the sky and ocean is due to the same reason (scattering of light) and it is not dependent on each other.