Explain why
Atmospheric pressure at a height of about 6km decreases to nearly half to its value at the sea level, through the height of the atmospheric is more than 100 km.

Atmosphere, hydrosphere, lithosphere and biosphere are the four main segments of the environment. Atmosphere is a cover of gases that extends to a height of about 1600 km above the surface of the earth and protects the life on the earth from harmful radiations coming from the sun or the outer space. Atmosphere is further divided into four regions such as troposphere, stratosphere, mesosphere and thermosphere. Hydrosphere forms that part of the environment which contains water. Lithosphere is the solid component of the earth consisting of soil, rocks, mountains etc. Biosphere is that part of the above segments where living organisms interact with these parts and live together. Which of the following is the coldest region ?

Atmosphere, hydrosphere, lithosphere and biosphere are the four main segments of the environment. Atmosphere is a cover of gases that extends to a height of about 1600 km above the surface of the earth and protects the life on the earth from harmful radiations coming from the sun or the outer space. Atmosphere is further divided into four regions such as troposphere, stratosphere, mesosphere and thermosphere. Hydrosphere forms that part of the environment which contains water. Lithosphere is the solid component of the earth consisting of soil, rocks, mountains etc. Biosphere is that part of the above segments where living organisms interact with these parts and live together. Hydrogen and Helium are found in which of the following regions ?