Question

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

Answer 1

actually, at higher altitudes the air column above decreases. so, the air will expand and then density decreases. Also at higher altitudes gravity is less because of which air molecules can spread freely. Hence density of air decreases with increasing altitude. therefore, density of air , 6km above the sea level < density of air at the sea level.
also , acceleration due to gravity at height 6km < acceleration due to gravity at sea level.

We also know that hydrostatic pressure is directly proportional to density of the fluid and the height of the liquid column above that level. P = ρgh
As both density of air and height of the air column 6 km above sea level are less compared to that at the sea level ,Atmospheric pressure decreases to nearly half of its value at 6 km above the sea level.

Answer 2

Answer:

it is because the density will be lower at sea level and therefore the pressure will be less