Atmospheris Pressure

• The envelope of air surrounding the earth is called atmosphere.
• It extends up to a height of about 800km.
• The density of air decreases as height increases.
• Air surrounds the earth because of the gravitational pull of the earth on it.
• The atmospheric pressure is caused by the weight of the air.
• “Once atmospheric pressure is the weight of the air exerted over an area of one square meter”.