ATMOSPHERE
ATMOSPHERE:-
The Earth Is Surrounded By
Blanket Of Air, Which We Call Atmosphere. It plays a significant role in the
life of living organisms on earth. Without atmosphere a living organism cannot
survive on earth. Hence, it is an important nature resource.
Atmosphere extends over 690
kilometers from the surface of the earth. It helps living organisms by,
providing important gases to them, protecting them from ultraviolet rays, by
providing rainfall, it helps in controlling the global warming and it acts like
a protector for the earth.
Atmosphere is a mixture of
various gases and dust particles. It mainly consists of 78% of nitrogen, 20.9%
of oxygen 1% of argon, carbon dioxide and other gases. The atmosphere will be
denser in the lower surface of the earth the upper layer. We can also say that
decrease in altitude, decrease in density of air and vise-versa.
There will be increase in
density of air as we increase the altitude because in higher altitudes the
upper layer pushes the air towards the down layer. This is the reason why it is
difficult to breath as we go to higher altitudes.
Atmosphere pressure depends
on three main factors:
1. Atitude 2. Temperature 3. Water vapour
(1) Altitude- The
preasure of the air deacreases. At a rate of 1cm for every 110metres of ascent.
(2)Temperature- When the temperature rises,air expands. At
the Equator as the area gets direct rays of sun.
(3) Water Vapour- Air containing water vapour is lighter than
dry air. The more water vapor, the lighter the air.
STRUCTURE OF ATMOSPHERE
Troposphere
Stratosphere
Mesosphere
Ionosphere/Thermosphere
Exosphere
(1) Troposphere
The term
troposphere literally means the region of mixing. It has been derived from the
Greek word tropos meaning mixing or turbulence. The average height of
troposphere is about 14Km above sea level. It is the lowermost atmospheric
layer closest to the earth. The degree at which water vapour is present in air
is called humidity.
(2) Stratosphere
The lowermost limit of stratosphere is at tropopause .This layer is free of water vapour and dust. It extends from 15 to 50Km between 50 to 60 latitudes. In this layer, the temperature does not change with latitude. The stratosphere is that it contains the ozone layer. There is maximum concentration of ozone, a vital gas between 20-30Km. This region is called ozonosphere.
(3) Mesosphere
This layer lies from
50 to 80 Km above the earth’ surface. Meteors from space mostly burn up in this
layer, creating shooting stars.
(4) Ionosphere/Thermosphere
Ionosphere extends from 80Km to
about 450 Km. Ionosphere reflects the low frequency radio waves, but absorbs
the median and high frequency waves. Thus, this layer is especially important
in long distance radio communication.
(5) Exosphere
This outermost layer
of atmosphere forms the outermost boundary of our atmosphere. The atmosphere in
this region is highly predominant with rarified hydrogen and helium.
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