Question

NCERT Solutions Class 11, Geography, Fundamentals of Physical Geography, Chapter-8, Solar Radiation, Heat Balance and Temperature

For success in board and competitive exams, it’s crucial to achieve a deep understanding of Class 11 Geography, and NCERT Solutions are a valuable tool. Developed by experts, these resources emphasize significant themes in each chapter while adhering to the CBSE curriculum, providing essential assistance in your academic journey.

In these NCERT Solutions for Class 11 Geography, we have discussed all types of NCERT intext questions and exercise questions.

Concepts covered in Class 11 Geography, Fundamentals of Physical Geography, Chapter- 8 Solar Radiation, Heat Balance and Temperature, are-

• Solar Radiation
• Variability of Insolation at the Surface of the Earth
• Terrestrial Radiation
• Heating and Cooling of Atmosphere
• Heat Budget of the Planet Earth
• Temperature
• Inversion of Temperature

Our NCERT Solutions for Class 11 Geography offer detailed explanations to assist you with homework and assignments. By mastering the concepts in each chapter through these solutions, you'll be well-prepared to achieve top marks in your exams. Start your journey to academic success today!

Quickly access all the solutions and practice questions you require to improve your study habits and prepare thoroughly for academic success.

Answer 1

NCERT Solutions Class 11, Geography, Fundamentals of Physical Geography, Chapter-8, Solar Radiation, Heat Balance and Temperature

1. Multiple choice questions.

(i) The sun is directly overhead at noon on 21st June at:

(a) The equator

(b) 23.5° S

(c) 23.5° N

(d) 66.5° N

Solution:

(c) 23.5° N

(ii) In which one of the following cities, are the days the longest?

(a) Tiruvanantpuram

(b) Chandigarh

(c) Hyderabad

(d) Nagpur

Solution:

(b) Chandigarh

(iii) The atmosphere is mainly heated by the:

(a) Short wave solar radiation

(b) Reflected solar radiation

(c) Long wave terrestrial radiation

(d) Scattered solar radiation

Solution:

(c) Long wave terrestrial radiation

(iv) Make correct pairs from the following two columns. 

Column I	Column II
(a) Insolation	i. The difference between the mean temperature of the warmest and the coldest months.
(b) Albedo	ii. The lines joining the places of equal temperature.
(c) Isotherm	iii. The incoming solar radiation.
(d) Annual range	iv. The percentage of visible light reflected by an object.

Solution:

(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i).

(v) The main reason that the earth experiences highest temperatures in the subtropics in the northern hemisphere rather than at the equator is:

(a) Subtropical areas tend to have less cloud cover than equatorial areas.

(b) Subtropical areas have longer day hours in the summer than the equatorial.

(c) Subtropical areas have an enhanced “green house effect” compared to equatorial areas.

(d) Subtropical areas are nearer to the oceanic areas than the equatorial locations.

Solution:

(a) Subtropical areas tend to have less cloud cover than equatorial areas.

2. Answer the following questions in about 30 words.

(i) How does the unequal distribution of heat over the planet earth in space and time cause variations in weather and climate?

Solution:

The sun provides almost all of the energy that the earth needs. The energy that the earth receives from the sun is then radiated back into space. As a result, throughout time, neither the earth’s temperature rises nor falls. As a result, not all regions of the globe experience the same amount of heat. This variation causes pressure difference in the atmosphere. As a result, heat is transferred by winds from one area to another. Thus, differences in weather and climate are brought on by the uneven distribution of heat over the globe Earth in both space and time.

(ii) What are the factors that control temperature distribution on the surface of the earth?

Solution:

The factors that cause these variations in insolation are:

(a) The rotation of earth on its axis.

(b) The angle of inclination of the sun’s rays.

(c) The length of the day.

(d) The transparency of the atmosphere.

(e) The configuration of land in terms of its aspect.

(iii) In India, why is the day temperature maximum in May and why not after the summer solstice?

Solution:

Tropic of Cancer on June 21 (summer solstice) India has started receiving its monsoon. It brings cooling effect to the climate of India, which was facing intense heat since March. As a result, the day temperature maximum in May and why not after the summer solstice.

(iv) Why is the annual range of temperature high in the Siberian plains?

Solution:

Because the Siberian Plains are positioned far from the ocean and equalising effect of ocean is relatively minimal, and this plains have a continental climate. As a result, the annual range of temperature remains high in the Siberian plains.

3. Answer the following questions in about 150 words.

(i) How do the latitude and the tilt in the axis of rotation of the earth affect the amount of radiation received at the earth’s surface?

Solution:

The sun has a significant impact on the quantity of insolation received at various latitudes when the earth’s axis forms an angle of 66.5 degrees with the plane of its orbit around the sun. Because of its inclination toward the sun in the month of June, the Northern Hemisphere experiences more solar radiation than the Southern Hemisphere.

Due to its inclination toward the sun in the month December, the southern hemisphere experiences more solar radiation than the northern hemisphere. The amount of heat produced by solar radiation on earth varies with latitude. For the majority of the year, the sun’s beams are practically vertical near the equator and at the poles. As a result, areas close to the equator experience greater solar radiation than those close to the poles.

(ii) Discuss the processes through which the earthatmosphere system maintains heat balance.

Solution:

The earth-atmosphere system maintains heat balance in different ways of heating and cooling of the atmosphere:

(a) Conduction:

1. After being heated by insolation, the earth radiates heat in the form of long waves in to the nearby atmospheric layers. The top layers in touch with the lower layers and the air in contact with the land both gradually warm up.
2. Energy flows from the warmer to the colder body when two bodies of different temperatures come into contact with one another. Heat is transferred until both bodies reach the same temperature or the contact is severed, whichever comes first.

(b) Convection: The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmosphere. This process of vertical heating of the atmosphere is known as convection. The convective transfer of energy is confined only to the troposphere

(c) Advection:

(a) Advection is the term used to describe the transmission of heat by horizontal air movement. The air’s horizontal movement is generally more significant than its vertical movement.

(b) In middle latitudes, advection alone is responsible for the majority of diurnal (day and night) variation in daily weather. Local winds known as “loo” are the result of the advection process and occur in tropical places, particularly in northern India during the summer.

(iii) Compare the global distribution of temperature in January over the northern and the southern hemisphere of the earth.

Solution:

The temperature distribution is generally shown on the map with the help of isotherms, the joining places having equal temperature.

(a) In general, the isotherms run parallel to the latitude.

(b) The land surface area in the northern hemisphere is significantly larger than in the southern hemisphere. As a result, the effects of land mass and ocean currents are quite noticeable.

(c) The isotherms diverge in January, moving to the north over the ocean and to the south over land. On the North Atlantic Ocean, this can be seen.

(d) The Gulf Stream and North Atlantic Drift, which are warm ocean currents, warm up the Northern Atlantic Ocean and cause the isotherms to curve toward the north. In Europe, the isotherms bend southward over the terrain as temperatures drop suddenly.

(e) In the Southern Hemisphere, the influence of the ocean is very noticeable. Compared to the Northern Hemisphere, the temperature variation is more gradual here since the isotherms are more or less parallel to the latitudes.

(f) The isotherm of 20°C, 10°C, and 0°C corresponds to latitudes of 35°S, 45°S, and 60°S, respectively.

Answer 2

More Questions

Multiple Choice Questions

1. What percent of sunrays that is received by the upper layer of the atmosphere reach the earth surface?

(a) 43%
(b) 51%
(c) 53%
(d) 40%

Solution:

(b) 51%

2. The process of heating up of land through horizontal movement of heat is called:

(a) Conduction
(b) Convection
(c) Advection
(d) Air drainage

Solution:

(a) Conduction

3. With increase in height the temperature decreases at a normal rate. It is called:

(a) Air drainage
(b) Earth radiation
(c) Normal lapse rate
(d) Inversion of temperature

Solution:

(c) Normal lapse rate

4. Being heavy and dense, the cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called what?

(a) Air drainage
(b) Earth radiation
(c) Normal lapse rate
(d) Inversion of temperature

Solution:

(a) Air drainage

5. The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmosphere. This process of vertical heating of the atmosphere is called what?

(a) Conduction
(b) Convection
(c) Advection
(d) Air drainage

Solution:

(b) Convection

6. What is normal lapse rate at 1000 metre?

(a) 4 degree Celsius
(b) 2 degree Celsius
(c) 1 degree Celsius
(d) 6.5 degree Celsius

Solution:

(d) 6.5 degree Celsius

7. On 4th July, the earth is farthest from sun. What is its distance?

(a) 152 million km
(b) 147 million km
(c) 148 million km
(d) 198 million km

Solution:

(a) 152 million km

8. On 3rd January, the earth is nearest from sun. What is its distance?

(a) 152 million km
(b) 147 million km
(c) 148 million km
(d) 198 million km

Solution:

(b) 147 million km

9. Which continent has highest temperature range?

(a) Asia
(b) Australia
(c) Africa
(d) Eurasia

Solution:

(d) Eurasia

10. Which of the following has longest day and nights?

(a) Poles
(b) Equator
(c) Tropic of Cancer
(d) Tropic of Capricorn

Solution:

(a) Poles

11. Which of the following causes inversion of temperature in mountainous regions?

(a) Due to air drainage
(b) Due to dust particles
(c) Due to gravitation
(d) Due to water vapours

Solution:

(a) Due to air drainage

Very Short Answer Type Questions

1. What factors cause variation in insolation?

Solution:

The factors that cause these variations in insolation are:

• the rotation of earth on its axis;
• the angle of inclination of the sun’s rays;
• the length of the day;
• the transparency of the atmosphere;
• the configuration of land in terms of its aspect.

2. What is aphelion?

Solution:

During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion.

3. What is perihelion?

Solution:

On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion.

4. What does Plank’s law state?

Solution:

Plank’s law states that hotter a body, the more energy it will radiate and shorter the wavelength of that radiation.

5. What factors affect the temperature of a place?

Solution:

The temperature of air at any place is influenced by

• the latituae of the place;
• the altitude of the place;
• distance from the sea, the air- mass circulation;
• the presence of warm and cold ocean currents;
• local aspects.

6. What is terrestrial radiation?

Solution:

The insolation received by the earth is in short wave orms and heats up its surface. The i arth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiatio”

7. What are the causes behind loo in tropical regions?

Solution:

In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.

8. Why does sun look red during rising and setting and why does sky look blue?

Solution:

Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation. Very small- suspended particles in the troposphere scatter visible spectrum both to the space and towards the earth surface.

This process adds colour to the sky. The red colour of the rising and the setting sun and the blue colour of the sky are the result of scattering light of the atmosphere.

9. How does some amount of energy is reflected to the atmosphere? or what is albedo?

Solution:

While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. Only the remaining part reaches the earth surface. The reflected amount of radiation is called the albedo of the earth.

10. How do sunrays while passing through atmosphere gets absorbed?

Solution:

Out of 100% received, 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence and 19 units through latent heat of condensation).

11. Atmosphere gets heated up indirectly by terrestrial radiation and not directly by sunrays. Explain.

Solution:

The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth's radiation. The atmosphere in turn radiates and transmits heat to the space. Finally, the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth.s surface and in the atmosphere.

12. What is meant by insolation?

Solution:

The earth’s surface receives most of its energy in short wavelengths. The energy received by the earth’s is known as incoming solar radiation which in short is termed as insolation.

13. Differentiate between Perihelion and Aphelion.

Solution:

During its revolution around the sun, the earth is farthest from the sun, on 4th July. This position of earth is called Aphelion.

And on 3rd January, the earth is the nearest to the sun. This position is called Perihelion.

14. Why the annual insolation received by the earth on 3rd January is more than that of 4th July?

Solution:

The solar output received at the top of atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. Therefore, the annual insolation received by the earth on 3rd January is more than the amount received on 4th July.

Answer 3

Short Answer Type Questions

1. What is inversion of temperature? When and in what regions does it take place?

Solution:

At times, the situations are reversed and the normal lapse rate is inverted. It is called Inversion of temperature. Inversion is usually of short duration but quite common nonetheless. A long winter night with clear skies and still air is ideal situation for inversion. The heat of the day is radiated off during the night, and by early morning hours, the earth is’ cooler than the air above. Over polar areas, temperature inversion is normal throughout the year. Surface inversion promotes stability in the lower layers of the atmosphere.

Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere. Dense fogs in mornings are common occurrences especially during winter season. This inversion commonly lasts for few7 hours until the sun comes up and beings to warm the earth. The inversion takes place in hills and mountains due to air drainage.

2. How does the energy received in upper layer of the atmosphere keep changing at different times of the year?

Solution:

The solar output received at the top of the atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion. On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion. Therefore, the annual insolation received by the earth on 3rd January is slightly more than the amount received on 4th July.

However, the effect of this variation in the solar output is masked by other factors like the distribution of land and sea, and the atmospheric circulation. Hence, this variation in the solar output does not have great effect on daily weather changes on the surface of the earth.

3. How does the amount of insolation received depends on the angle of inclination of the rays?

Solution:

The amount of insolation received depends on the angle of inclination of the rays. It depends on the latitude of a place. The higher the latitude the less is the angle they make with the surface of the earth resulting in slant sunrays. The area covered by vertical rays is always less than the slant rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases. Moreover, the slant rays are required to pass through greater depth of the atmosphere resulting in more absorption, scattering and diffusion.

4. Explain about spatial distribution of insolation on the earth’s surface.

Solution:

The insolation received at the surface varies from about 320 Watt/m² in the tropics to about 70 Watt/m² in the poles. Maximum latitude insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics. Generally, at the same latitude the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.

5. Explain the distribution of temperature in July.

Solution:

Distribution of temperature in July:

• During this period the sun shines vertically over head near the tropic of cancer. It is summer for the northern hemisphere and winters for the southern hemisphere.
• In the northern hemisphere the isotherm bends equator wards while crossing the oceans and pole wards ‘while crossing the landmass. In the southern hemisphere it is vice-versa.
• The isotherms are most irregular and zig-zig in northern hemisphere on the other hand the isotherms are relatively more regular and straight in southern hemisphere.
• Maximum temperature of about 30 degree centigrade occurs entirely in the northern hemisphere between 10° and 40° north latitude however the lowest temperature below 0° C is recorded over northern hemisphere in the central parts of green land.

6. Explain the factors affecting insolation at the surface of earth.

Solution:

The factors affecting insolation at the surface of earth are:-

1) The rotation of earth on its axis: The fact that the earth on its axis makes an angle of 6614 with the plane of it’s orbit round the sun has a greater influence on the amount of insolation received at different latitudes.

2) The angle of inclination of the sunrays: The higher the latitude the greater is the angle they make with the surface of the’earth resulting in slant sunrays. The areas covered by vertical rays is always less than the slant rays. If more areas is covered the energy gets distributed and the net energy received per unit area decreases. Thus, the slant rays are required to pass through greater depth of the atmosphere resulting in more absorption, scattering and diffusion.

3) The transparency of the atmosphere: The atmosphere is largely transparent to the short wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation.

4) The configuration of land in terms of its aspect: The insolation received at the surface varies from about 320 watt/ m2 in the poles. Maximum insolation is received over the subtropical deserts, when the cfoudness is the least. Equator receives less rainfall as compared to tropics

7. Distribution of temperature in the month of July.

Solution:

• During this period the sun shines vertically over head near tropic of cancer it is the summer for northern hemisphere and winter for southern hemisphere.
• The isotherms are relatively more regular and straight in southern hemisphere.
• Maximum temperature of over 30°C occurs entirely in northern hemisphere between 10° and 40° temperature below 0° C is recorded over northern hemisphere in the central parts of Greenland.

8. Explain the distribution of temperature in January.

Solution:

1. In January the isotherms deviate to north over the ocean and to the south over the continent. This can be seen on the North Atlantic Ocean.

2. The pressure of warm ocean currents, Gulf Stream and north Atlantic drift, make the northern Atlantic Ocean warmer and the isotherms bend towards the north.

3. Over the land the temperature decreases sharply and the isotherms bend towards south in Europe.

4.  It is much pronounced in the Siberian plan. The mean January temperature along 60° E longitude is minus 20° both at 80° N and 50° N latitude. The mean monthly temperature for January is over 27° C in equatorial oceans over 24°C in the tropics and 2° C- 0° C in middle latitudes and -18° C to -48° C in Eurasian continental interior.

5. The effect of the ocean in well pronounced in southern hemisphere. Here, the isotherms are more or less parallel to latitudes and the variations in temperature is more gradual than in the northern hemisphere. The isotherm of 20°C, 10°C, and 0°C run parallel to 35°S, 45° and 60°S latitudes respectively.

Answer 4

Long Answer Type Questions

1. Explain about inversion of temperature.

Solution:

At times, the situations are reversed and the normal lapse rate is inverted. It is called inversion of temperature. Inversion is usually of short duration but quite common nonetheless. A long winter night with clear skies and still air is ideal situation for inversion. The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above.

Over polar areas, temperature inversion is normal throughout the year. Surface inversion promotes stability in the lower layers of the atmosphere. Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere. Dense fogs in mornings are common occurrences especially during winter season. This inversion commonly lasts for few hours until the sun comes up and beings to warm the earth. The inversion takes place in hills and mountains due to air drainage.

2. Explain the heating and the cooling mechanism of atmosphere.

Or

Discuss the process through which earth and the atmosphere system maintain heat balance.

Solution:

(a) Conduction:

• The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated.
• Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere.

(b) Convection:

• The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmosphere. This vertical heating of atmosphere is known as convection.
• The convection transfer of energy is confined only to the troposphere.

(c) Advection:

• The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important than the vertical movement.
• In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.

Hots Questions

1. Explain about heat budget of the earth.

Solution:

The earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from the sun. As a result, the earth neither warms up nor does it get cooled over a period of time. Thus, the amount of heat received by different parts of the earth is not the same. This variation causes pressure differences in the atmosphere. This leads to transfer of heat from one region to the other by winds. The insolation received at the top of the atmosphere is 100 per cent. While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. Only the remaining part reaches the earth surface.

Roughly 35 units are reflected back to space even before reaching the earth’s surface. Of these, 27 units are reflected back from the top of the clouds and 2 units from the snow and ice- covered areas of the earth. The reflected amount of radiation is called the albedo of the earth. The remaining 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence and 19 units through latent heat of condensation). 48 units absorbed by the atmosphere (14 units from insolation +34 emits from terrestrial radiation) are radiated back into space.

MAP SKILL

1. On an outline map of the world, locate the distribution of surface air temperature in the month of January.

Solution: