Question

The colour of the sky is due to:
A. Transmission of light.
B. Wavelength of scattered light.
C. Absorption of light by atmospheric gases.
D. All of these.

Answer 1

Hint: We know that white light is a combination of the 7 rainbow colours( red, orange, yellow, green, blue, indigo and violet). When white light passes through a medium it can be reflected, refracted or can be split into these colours.

Complete step by step solution:
Earth’s atmosphere consists of many gas molecules and dust particles. When the sunlight passes through this atmosphere, it is scattered by these gas molecules and dust particles. Let us understand more how the light is scattered.
-We know that sunlight is white in colour, but it is actually made up of a combination of the colours of the rainbow.
-To get the various colours of the white light, we can pass the white light through a prism.
-Usually light travels in a straight line unless there is something in its way. For example: it is reflected (by a mirror), bent (by a prism) , or scattered.
-The visible part of the spectrum ranges from red (wavelength 720nm) to violet (wavelength 380nm).
-The sky is mostly blue in colour because it is the most scattered light in the visible spectrum. This is due its short wavelength (490-450 nm) compared to the other colours of visible spectrum.
The visible spectrum of the sunlight is scattered by the molecules and gases in the air to give colour to the sky. Hence the answer to this question is option(b) wavelength of scattered light.

Note: It is often mistaken that the colour of the sky is due to the absorption of light by atmospheric gases and they emit the complementary colour which we are able to see through naked eye. But this is not the case. It is mainly due to the scattering of sunlight by the particles and molecules in the atmosphere.