Question 1:
Which one of the following is the most important constituent of the atmosphere for human beings?
- Water vapour
- Dust particle
- Nitrogen
- Oxygen
Answer:
(d). Oxygen
Question 2:
Which one of the following process is responsible for transforming liquid into vapour?
- Condensation
- Evaporation
- Transportation
- Precipitation
Answer:
(b). Evaporation
Question 3:
The air that contains moisture to its full capacity :
- Relative humidity
- Absolute humidity
- Specific humidity
- Saturated air
Answer:
(c). Saturated air
Question 4:
Which one of the following is the highest cloud in the sky?
- Cirrus
- Nimbus
- Stratus
- Cumulus
Answer:
(a). Cirrus
Question 5:
Name the three types of precipitation.
Answer:
(1) Rainfall
(2) Snowfall
(3) Hail.
Question 6:
Why does the amount of water vapour decreases rapidlly with altitude?
Answer:
There is absence of sources of water at greater heights. The temperature also decreases with heights. So the evaporation is also low.
Question 7:
How are clouds formed? Classify them.
Answer:
Clouds are formed by condensation of water
vapour.
Clouds are classified into three groups according to
their height :
(a) High Clouds. (Above 6 km.) Cirrus clouds are
high clouds. It has a feathery appearance.
(b) Medium Clouds. (2 km. to 6 km.) Cumulus clouds
are medium clouds. These are wooly and whitish clouds.
(c) Low Clouds. (Below 2 km). Nimbus clouds are
low clouds. These dark grey clouds give rain.
Question 8:
Discuss the salient features of the world distribution of precipitation.
Answer:
Distribution of rainfall. The distribution of
rainfall is shown according to latitudes. This is known
as zonal distribution.
(1) The average annual precipitation for the whole
earth is about 975 m.m. On the land it is about 660
m.m., but on the ocean it is about 1100 m.m.
(2) The maximum annual rainfall is about 1900 m.m.
and it occurs in the equatorial zone between 10° N —
10° S latitudes.
(3) Between 20° — 30° latitudes, the average annual
rainfall is 800 m.m.
(4) Between 45° — 55° latitudes, the average annual
rainfall is minimum about 1000 m.m.
(5) Beyond 75° North and South latitude, the average
rainfall is minimum about 250 m.m. only.
(6) The continental interiors get low rainfall as
compared to coastal areas.
(7) Trade winds give rainfall in eastern parts of the
tropics.
(8) The westerlies give rainfall in the west in the
temperate latitudes.
Question 9:
What are forms of condensation? Describe the process of dew and frost formation.
Answer:
Condensation
Condensation in the process by which water vapour
of the atmosphere is changed to water (from gaseous to
liquid state). With the fall of temperature or cooling of
air, its capacity to hold water vapour is lowered. The air
is saturated when dew-point is reached. Condensation
starts when the temperature falls below dew-point. Then
the excess of water is released or condensed into a liquid
form.
Condensation takes place :
(i) When the air rises, expands and cools due to
adiabatic temperature changes.
(ii) When moist laden wind strikes against a
mountain and is forced to ascend.
(iii) When two warm and cold air masses meet.
Forms of Condensation. Condensation takes place
in different forms such as :
(i) frost and snow.
(ii) dew, fog, mist and smog.
(iii) clouds and haze.
(i) Clouds : When the air usually at a considerable
height above the earth’s surface is cooled, condensation
takes place in it. As a result, a mass of small water
drops is formed. This is called cloud. Clouds are formed
when air carrying moisture is lifted upwards and cooled
as it rises. The condensed water droplets cling to the
dust particles in the air and thus reduce the visibility.
clouds assume an almost infinite variety of forms. They
have been classified according to their shape and
altitude.
(ii) Fog : When the air near the earth’s surface is
cooled throughout, condensation takes place in it. Small
drops of water are formed and they cling to the dust
particles which float in the air and reduce the visibility.
This is called mist and if it is very thick then it is known
as fog. The visibility in the mist is more than one
kilometre, while in fog it is less than one kilometre. Fog
when formed at a considerable height above the earth’s
surface is termed as cloud. Fog formed on smoke is called
smog.
(iii) Rain : When moisture-laden air rises up,
condensation takes place and clouds are formed. If the
clouds are further cooled, there is more condesation
and drops of water that are formed are big in size. These
big drops are too heavy to remain hanging in the air
and fall down towards the earth’s surface. The falling
of these drops of water from the clouds is known as
rain.
(iv) Snowfall : If condnsation takes place at a
temperature below freezing point (0° Celsius), the
water-vapour condenses into small crystals of ice
instead of drops of water. These small crystals then
unite to form flakes of ice called snow. The coming
down of snowflakes towards the earth’s surface is known
as snowfall.
(v) Hail : Sometimes rain-drops on their way to the
earth’s surface are carried by strong air currents upward
into colder regions. This causes the rain-drops to freeze.
After freezing, they collect more water which too freezes.
Thus they grow in size and become heavy. They become so
big and heavy that the air can no longer hold them.
Therefore, they fall back to the earth’s surface as hailstones.
(vi) Dew : When the temperature of the air is higher