Question

Assertion
The planet Neptune appears blue in colour.
Reason
The presence of methane gas in the atmosphere of Neptune is responsible for its colour.
A.Both assertion and reason are correct and reason is the correct explanation for assertion.
B.Both assertion and reason are correct, but reason is not the correct explanation for assertion.
C.Assertion is correct, but reason is incorrect.
D.Assertion is incorrect, but reason is correct.

Answer 1

Hint: The colour to any planet is because of the scattering of white by its major gas composition which on absorbing the light of certain wavelength reflects the light of another colour. The wavelength of the blue colour is short, so scattering of this wavelength is quite high.

Complete step by step answer:
Neptune is the outermost planet of our solar system and is the eight planet in the sequence. By considering the diameter of planet Neptune it is the fourth largest planet, in comparison to the mass of planet earth the mass is seventeen times than earth.
Composition: The properties of each substance, planet or area is depicted by the particles or gases prevailing in that area. The major constituents of planet Neptune are methane, helium and hydrogen gas, and the methane gas plays an important role in providing colour to the planet Neptune.
We know that when a white light is passed through the prism it gets converted into seven colours known as VIBGYOR, which represents the colour of rainbow. The same phenomena happens here when the white light is passed through the methane gas molecules, molecules they absorb the red light and reflects the blue light from them which imparts the blue colour to its environment. The scattering of blue light is maximum because in VIBGYOR, the increasing order of wavelength is seen and blue colour has the shorter wavelength which scatters the most.
Thus the assertion statement is true and the reason statement is also true which says that the Neptune planet is blue in colour because of the presence of the methane gas in its environment.

So, the correct answer is Option A .

Note:
Scattering process involves the splitting of white light in its constituents. Each particle in nature has the ability to absorb a certain wavelength and emit that wavelength in increased or decreased ratio. This process is responsible for the coloured nature of our environment.