Question

The planet known as the ‘blue planet’ is the _ _ _ _ _ _
A. Earth
B. Mars
C. Jupiter
D. Pluto

Answer 1

Hint: The name can be derived from the colour of the planet as seen from outer space. The blue colour can be attributed to the water bodies present on the planet. So, earth which consists of mostly oceans and seas, will appear blue in outer space.

Complete step by step answer:
Earth is known as the blue planet. This is because the two-third of the earth consists of water bodies like oceans and seas. When the sunlight which consists of all the wavelengths hits the water molecules in the seas and oceans, most of the wavelength which belongs to the infrared, red and ultraviolet range is absorbed by the molecules and what is left is the blue wavelength, which is reflected off the water surface. This blue wavelength is responsible for the blue colour of the earth.
So, the answer to the question is option (A).
Additional Information:
Neptune is another blue planet in our solar system whose atmosphere is made up of hydrogen, helium and methane. Methane is responsible for the blue colour of the planet. This is because methane in gaseous form absorbs all the red wavelength from the sun and only reflects blue wavelengths.

Note: Mars is called the red planet. Due to iron content in its soil, the mars surface is red in colour.
The sky is blue because the atmosphere scatters shorter wavelengths like the blue colour ore easily than the longer wavelength. As a result, the sky appears blue.
Only 11 percent of the incident sunlight is reflected back to the atmosphere from the water bodies.