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Chapter 13

Insolation

Class 9 - Total Geography Morning Star


Short Answer Questions

Question 1

What is solar radiation? What is its significance for the Earth?

Answer

The Sun continuously radiates heat and light energy in all the directions. It is known as solar radiation.

Solar radiation is the only primary source of light and heat on the Earth. The Earth receives its heat from solar radiation which is a tiny fraction of the radiated energy of the Sun.

Question 2

What is meant by insolation? State two of its main characteristics.

Answer

The amount of solar energy received by the Earth is called insolation.

Two main characteristics of insolation are-

  1. The Sun's energy reaches the Earth as short wave rays.
  2. Out of the total 100% solar energy, only 51% reaches the Earth, 35% is reflected back into space and only 14% is absorbed by the atmospheric layers including the ozone during insolation.

Question 3

State two advantages of convectional heating of the atmosphere.

Answer

Two advantages of convectional heating of the atmosphere are-

  1. At night, the atmosphere acts as a greenhouse and keeps the Earth's surface warm by preventing the terrestrial radiation from escaping into space.
  2. During the day, the atmosphere absorbs 14% of insolation and thus regulates temperature on Earth.

Question 4

Name four factors that affect the temperature of a place.

Answer

Four factors that affect the temperature of a place are-

  1. Latitude of a place
  2. Altitude of a place
  3. Distance from the sea
  4. Slope of the land

Question 5

State the pattern of temperature in mid latitudes.

Answer

Due to spherical shape of the Earth, mid latitudes get less insolation resulting in moderate climate with normal temperature ranging from 15°C to 30°C. The duration of sunshine is greater in summer than winter. So the summer is warm and winter is cold.

Question 6

What difference is there in the temperatures on a mountain and on a sea shore?

Answer

Temperature keeps on decreasing with increase in altitude. There is a fall of 1°C in temperature on climbing every 166 metres. Hence, the temperature on a mountain is lower than the temperature on a sea shore.

Question 7

Why is India cooler in December than in July?

Answer

The Tropic of Cancer passes mid-way across India. On June 21, the rays of the Sun falls directly over the Tropic of Cancer as the North Pole get tilted towards the Sun. The southern hemisphere is tilted away from the Sun during this time. Hence, July is hot.

On December 22nd, the Southern Hemisphere is tilted towards the Sun and the Sun rays fall vertically over the Tropic of Capricorn, while the Northern Hemisphere is tilted away from the Sun. So, India, which lies in the Northern Hemisphere experience winters in December.

Distinguish between each of the following

Question 1

Insolation and Terrestrial Radiation

Answer

InsolationTerrestrial Radiation
The amount of solar energy received by the Earth is called insolation.The heat radiated by the Earth in the form of long waves is called terrestrial radiation.
The Sun's energy reaches the Earth as short waves.Terrestrial radiation is radiated in the form of long waves.

Question 2

Land breeze and sea breeze

Answer

Land breezeSea breeze
It blows from land to sea.It blows from sea to land.
It blows at night.It blows during day time.
It is dry and does not contain much moisture.It is laden with moisture.
It generally has no effect on temperature.It moderates the climate of the coastal parts.

Structured Questions

Question 1(a)

How is 'heat balance' achieved?

Answer

The atmosphere absorbs 34 units of the Earth's radiation, but it absorbs only 14 units of the Sun's incoming radiation. Thus, the atmosphere is heated more by terrestrial radiation given out by the Earth than by the incoming insolation from the Sun.

At night, the atmosphere acts as a greenhouse and keeps the Earth's surface warm by preventing the terrestrial radiation from escaping into space. During the day, the atmosphere absorbs 14% of insolation and thus regulates temperature on Earth.

Question 1(b)

State how latitude affects the temperature of a place.

Answer

The temperature of a place depends on the latitude of a place as temperature decreases with increase in latitude on either side of the equator due to the spherical shape of the Earth and its annual revolution around the Sun.

Also, the mid day Sun is almost overhead within the tropics but at oblique angles outside the tropics.

Question 1(c)

Give a reason for each of the following:

(i) North India has a greater range of temperature than South India.

(ii) The temperature of Delhi is less than that of Chennai in December.

(iii) Desert areas experience a high day temperature and a much lower night temperature.

Answer

(i) North India lies away from the water bodies and experiences continental type of climate whereas South India being near the water bodies experiences maritime climate. Also, North India comes in temperate zone as it lies towards the north of Tropic of Cancer whereas South India falls in Torrid Zone towards the south of Tropic of Cancer. Due to these reasons, North India has a greater range of temperature than South India.

(ii) The temperature of Delhi is less than that of Chennai in December because Delhi lies beyond the Tropic of Cancer, in the Temperate zone. So in December, it receives slanting rays of the sun. But Chennai is located in Torrid zone and hence, it receives vertical rays of the sun throughout the year. Therefore, the temperature of Delhi is lesser during the December.

(iii) Desert areas experience a high day temperature and a much lower night temperature because desert areas are covered with sand. The physical property of the sand is to get heated up quickly and cool down abruptly. So, the day temperature is very high and the night temperature is very low.

Question 1(d)

Draw a well labelled diagram to show the Heat Budget of the Earth.

Answer

Below labelled diagram shows the Heat Budget of the Earth:

Draw a well labelled diagram to show the Heat Budget of the Earth. Insolation, Total Geography Solutions ICSE Class 9.

Question 2(a)

State the five temperature zones of the Earth.

Answer

The five temperature zones of the Earth are-

  1. Torrid Zone
  2. North Temperate Zone
  3. South Temperate Zone
  4. North Frigid Zone
  5. South Frigid Zone

Question 2(b)

Explain the Normal Lapse Rate.

Answer

The rate of decrease of temperature with height is about 6°C per km above the sea level, so on climbing every 166 metres, there is a fall of 1°C in temperature. It is known as Normal Lapse Rate.

Question 2(c)

Give a reason for each of the following:

(i) Distance from the sea affects the temperature of a place.

(ii) Land is heated and cooled faster than the sea.

(iii) The ports of the western coast of Europe remain ice-free during winter.

Answer

(i) Distance from the sea affects the temperature of a place as the sea breeze blowing from the sea towards the land cools the coastal regions during the day. At night, the land breeze makes the sea cooler. This interchange of breeze maintains the heat balance. Hence, the areas close to the sea have a lower daily and annual ranges of temperatures and enjoy a moderate climate than the areas lying in the interior.

(ii) Land is heated and cooled faster than the sea because water is mobile and the warm water mixes easily with the cold water and is neither heated nor cooled quickly. On the other hand, the Sun's rays heat a piece of land more rapidly because unlike water, the heat obtained by the area remains confined to that area and does not mix with other areas of land.

(iii) The ports of the western coast of Europe remain ice-free during winter due to the warm effect of the Gulf Stream and North Atlantic Drift.

Question 2(d)

Draw a well labelled diagram showing that the vertical rays are hotter than slanting rays.

Answer

Below labelled diagram shows that the vertical rays are hotter than slanting rays:

Draw a well labelled diagram showing that the vertical rays are hotter than slanting rays. Insolation, Total Geography Solutions ICSE Class 9.

Question 3(a)

How does the distance from the sea affect the distribution of temperature?

Answer

Distance from the sea affects the temperature of a place as the sea breeze blowing from the sea towards the land cools the coastal regions during the day. At night, the land breeze makes the sea cooler. This interchange of breeze maintains the heat balance. Hence, the areas close to the sea have a lower daily and annual ranges of temperatures and enjoy a moderate climate than the areas lying in the interior.

Question 3(b)

How would the breezes that blow during the day and those that blow during the night affect the temperature of a place situated in the coastal region?

Answer

During the day the sea breeze blowing towards the land from the sea keeps the coastal region cool and during the night the land breeze blowing from the land towards the sea makes the sea cooler.

This interchange of breeze maintains the heat balance. Hence, the areas close to the sea have a lower daily and annual ranges of temperatures and enjoy a moderate climate than the areas lying in the interior.

Question 3(c)

Give a reason for each of the following:

(i) Higher the latitude, lower is the temperature.

(ii) The vertical rays of the Sun give more insolation than the slanting rays.

(iii) A desert region has a high range of temperature than a forest region.

Answer

(i) At higher latitudes, the rays of the Sun fall in an oblique way. Oblique rays not only travel a longer distance, but also heat a larger area. Thus, they have less heating power. Hence, with higher latitudes, the temperature goes on decreasing.

(ii) The vertical rays of the Sun give more insolation than the slanting rays because vertical rays travel a shorter distance and heat up a smaller surface area leading to higher temperatures whereas slanting rays not only travel a longer distance, but also heat a larger area. Thus, they have less heating power.

(iii) Hot deserts have no cloud cover, which allows high insolation during the day and rapid loss of heat due to terrestrial radiation at night resulting in high range of temperature. On the other hand, forests absorb 9O% insolation and the solar energy absorbed by plants is used in the process of transpiration resulting in low range of temperature.

Question 3(d)

Draw a well labelled diagram to show the land and sea breeze.

Answer

Below labelled diagram shows the land and sea breeze:

Draw a well labelled diagram to show the land and sea breeze. Insolation, Total Geography Solutions ICSE Class 9.
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