- An atmosphere is a layer of gases surrounding a planet or other material body of sufficient mass that is held in place by the gravity of the body.
- The envelope of air that completely surrounds the earth is known as atmosphere. The atmosphere extends to about 1000 from the surface of the earth. But 99% of the total mass of the atmosphere is found within 32 km. This is because the atmosphere is held by the gravitational pull of the earth.
- Nitrogen – 78%
- Oxygen – 20.93% ~ 21%
- Argon -0.93%
- Carbon-dioxide – 0.03%
- Neon – 0.0018%
- Helium – 0.0005%
- Ozone – 0.0006%
- Hydrogen – 0.00005%
Carbon dioxide is present in small quantity in the atmosphere
It is an important constituent of air because it has the ability to absorb heat and thus keep the atmosphere warm, thereby, balancing the heat of the earth.
Dust intercepts and reflect incoming insolation.
The polluted particles present in the air not only absorb larger amount of insolation but also greatly absorb the terrestrial radiation. Dust in the atmosphere contributes to the red and orange colour of sunrise and sunset.
Layers of the Atmosphere
There are five distinct layers of the atmosphere –
- Thermosphere / Ionosphere