Explain the activity 14.2 of chapter "natural resources" . please it urgent

Dear student,
Please find below the solution to the asked query

The given activity explains abut the formation of convection currents and explains about the various movements of air in the atmosphere due to uneven heating of earth by sun that results in various phenomenon like formation of wind, climate change etc. 

In this activity, a burning candle is placed in a beaker. Then an incence stick is placed at its mouth. Following observations are made:

a) The smoke is pulled inside the beaker when the incense stick is kept at the mouth of the beaker.
b) The smoke moves upward when the incense stick is kept above the flame because hot air from the flame rises upwards.
c) The smoke flows towards the bottom of the flame when the stick is kept at the edge as air is required for combustion of wax.

From the experiment we can conclude that there is convection in air, the cold air is taken inside the beaker and hot air is given out.  

This can be further explained as:

Wind can be defined as the air that moves horizontally over Earth’s surface. Winds are formed as a result of the differential heating of the air in the atmosphere. A part of the solar radiation that reaches Earth’s surface is radiated back into the atmosphere. This heats up the atmosphere. The extent of this heating up of the atmosphere varies across land and water.

What is the direction of wind? Wind flows horizontally from a high pressure zone to a low pressure zone.

How are these high pressure and low pressure zones created?

Formation of winds during the day

As is observed in coastal regions, solar radiations heat up land faster than the sea. Consequently, the air above land becomes hot faster and then moves upward. As the air rises, it expands and cools down. This vertical movement of air is known as convection current. The convection current causes a lowpressure area to be created over land. 

Meanwhile, a high pressure area is formed over the watery surface. This is because the air over the sea is relatively cooler and so, does not move upward. 

The rising hot air leaves behind a vacant space above land. The air present over water moves toward this vacant space to occupy it. In other words, wind blows from the high pressure area over the sea to the low pressure area over land.

Hope this information will clear your doubts about the activity.
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