CHAPTER 11 : Water in the Atmosphere NCERT SOLUTION CLASS 11TH GEOGRAPHY| EDUGROWN NOTES

SHORT ANSWER TYPE QUESTION:

Q1. Name the three types of precipitation.
Answer
The three types of precipitation are:• Rainfall:  The precipitation in the form of water.• Snowfall:  The precipitation in the form of fine flakes of snow.• Hailstones: Sometimes, drops of rain after being released by the clouds become solidified into small rounded solid pieces of ice and which reach the surface of the earth.

Q2. Explain relative humidity.
Answer
The percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature is known as the relative humidity. 

Q3. Why does the amount of water vapour decreases rapidly with altitude?
Answer

The water vapour is greater over the oceans and least over the continents. There is absence of these water bodies on high altitudes. Temperature decreases with higher altitudes, therefore, rates of evaporation also decreases as a result water vapour also decreases rapidly with altitude.

Q4. How are clouds formed? Classify them.

Answer

Cloud is a mass of minute water droplets or tiny crystals of ice formed by the condensation of the water vapour in free air at considerable elevations.
According to their height, expanse, density and transparency or opaqueness clouds are grouped under four types :
• Cirrus
• Cumulus
• Stratus
• Nimbus.

Q5.Discuss the salient features of the world distribution of precipitation.

Answer

Different places on the earth’s surface receive different amounts of rainfall in a year and that too in different seasons.
• The rainfall decreases as we go from equator towards poles.
•  The coastal areas of the world receive greater amounts of rainfall than the interior of the continents. • The rainfall is more over the oceans than on the landmasses of the world because of being great sources of water.
• Between the latitudes 35° and 40° N and S of the equator, the rain is heavier on the eastern coasts and goes on decreasing towards the west.
• Between 45° and 65° N and S of equator, due to the westerlies, the rainfall is first received on the western margins of the continents and it goes on decreasing towards the east.
• Wherever mountains run parallel to the coast, the rain is greater on the coastal plain, on the windward side and it decreases towards the leeward side

Q6.What are forms of condensation? Describe the process of dew and frost formation.

Answer

The transformation of water vapour into water is called condensation. Condensation is caused by the loss of heat.

The forms of condensation are dew, frost, fog and clouds.

Formation of dew: When the moisture is deposited in the form of water droplets on cooler surfaces of solid objects such as stones, grass blades and plant leaves, it is known as dew. The ideal conditions for its formation are clear sky, calm air, high relative humidity, and cold and long nights. For the formation of dew, it is necessary that the dew point is above the freezing point.

Formation of frost: Frost forms on cold surfaces when condensation takes place below freezing point i.e. the dew point is at or below the freezing point. The excess moisture is deposited in the form of minute ice crystals instead of water droplets. The ideal conditions for the formation of white frost are the same as those for the formation of dew, except that the air temperature must be at or below the freezing point.

Long Answer Type Questions :

Q1.Explain about condensation in detail.
Answer:
1. Meaning: The transformation of water vapour into water is called condensation. Cause: Condensation is caused by the loss of heat.

2. Sublimation: When moist air is cooled, it may reach a level when its capacity to hold water vapour ceases. Then, the excess water vapour condenses into liquid form. If it directly condenses into solid form, it is known as sublimation.

3. Process: In free air, condensation results from cooling around very small particles termed as hygroscopic condensation nuclei. Particles of dust, smoke and salt from the ocean are particularly good nuclei because they absorb water. Condensation also takes place when the moist air comes in contact with some colder object and it may also take place when the temperature is close to the dew point. Condensation, therefore, depends upon the amount of cooling and the relative humidity of the air.

Factors affecting condensation:

• When the temperature of the air is reduced to dew point with its volume remaining constant;
• When both the volume and the temperature are reduced;
• When moisture is added to the air through evaporation.

However, the most favourable condition for condensation is the decrease in air temperature. After condensation the water vapour or the moisture in the atmosphere takes form of dew, frost, fog and clouds.

Q2.Explain about fog and mist.
Answer:
When the temperature of an air mass containing a large quantity of water vapour falls all of a sudden, condensation takes place within itself on fine dust particles. So, the fog is a cloud with its base at or very near to the ground.

• Because of the fog and mist, the visibility becomes poor to zero. In urban and industrial centres smoke provides plenty of nuclei which help in the formation of fog and mist.
• Such a condition when fog is mixed with smoke, is described as smog.
• The only difference between the mist and fog is that mist contains more moisture than the fog.
• In mist each nuceli contains a thicker layer of moisture. Mists are frequent over mountains as the warm air rises up the slopes and meets a cold surface.
• Fogs are drier than mist and they are prevalent where warm currents of air come in contact with cold currents. Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke, and the salt particles.