CBSE Class 11 Geography Chapter 9: Solar Radiation, Heat Balance, and Temperature NCERT Solutions

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NCERT Solutions PDF Class 11 PDF

This chapter delves into the fundamental concepts of solar radiation, heat balance, and temperature variations on Earth, crucial for understanding Geography. The NCERT Solutions for Class 11 Geography, Chapter 9, provide clear explanations and answers to key questions. It covers topics such as the direct overhead position of the sun on specific dates, factors influencing day length in different cities, the primary mechanisms heating the Earth's atmosphere, and the definitions of insolation, albedo, isotherms, and annual temperature range. The solutions also explore reasons for temperature variations between equatorial and subtropical regions and the impact of uneven heat distribution on weather and climate. These solutions are designed to help students grasp complex geographical principles and prepare thoroughly for their examinations.

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BoardCBSE
ClassClass 11
SubjectGeography
Session2026
LanguageEnglish
TypeNCERT Solutions
Chapter9. Solar Radiation Heat Balance and Temperature

Chapter summary

Chapter 9 of the Class 11 Geography syllabus focuses on Solar Radiation, Heat Balance, and Temperature. The NCERT Solutions provided here clarify concepts like the angle of incidence of solar radiation at different latitudes and times, factors affecting day length, and the process by which the atmosphere is heated. It also defines key terms such as insolation, albedo, isotherms, and annual temperature range, and explains the geographical reasons behind temperature differences between the equator and subtropics, and how uneven heat distribution influences weather and climate patterns.

Learning outcomes

  • Understand the concept of solar radiation and its distribution on Earth.
  • Explain the factors that determine the Earth's heat balance.
  • Define and differentiate between insolation, albedo, isotherms, and annual temperature range.
  • Analyze the reasons for temperature variations across different latitudes.
  • Describe how uneven heat distribution affects weather and climate.

Topics covered

Paper topics

  • Solar Radiation
  • Heat Balance
  • Temperature
  • Insolation
  • Albedo
  • Isotherms
  • Annual Range of Temperature
  • Earth's Heat Budget
  • Latitude and Temperature
  • Equatorial vs. Subtropical Temperatures
  • Weather and Climate Variations

Important topics

  • Insolation and its factors
  • Earth's Heat Balance
  • Albedo effect
  • Temperature distribution and its causes
  • Difference between weather and climate

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Questions and Solutions

Multiple choice question

(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: The sun is directly overhead at the Tropic of Cancer (23.5° N) on June 21st, which marks the summer solstice in the Northern Hemisphere. This is when the Northern Hemisphere is tilted most directly towards the sun.

Multiple choice question

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

(a) Tiruvanantpuram

(b) Chandigarh

(c) Hyderabad

(d) Nagpur

Solution: Days are longest in cities located at higher latitudes during summer. Among the given options, Chandigarh is situated at the highest latitude (approximately 30.7° N), hence it experiences the longest days compared to Tiruvanantpuram (approx. 8.5° N), Hyderabad (approx. 17.4° N), and Nagpur (approx. 21.1° N).

Multiple choice question

(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: The Earth's surface absorbs short-wave solar radiation and warms up. It then radiates this heat back into the atmosphere as long-wave terrestrial radiation. This long-wave radiation is effectively absorbed by greenhouse gases in the atmosphere, leading to its primary heating.

Multiple choice question

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

Column I

(i) Insolation

(ii) Albedo

(iii) Isotherm

(iv) Annual range

Column II

(a) The difference between the mean temperature of the warmest and the coldest months

(b) The lines joining the places of equal temperature

(c) The incoming solar radiation

(d) The percentage of visible light reflected by an object

Solution: The correct pairs are:
  1. Insolation (c) The incoming solar radiation
  2. Albedo (d) The percentage of visible light reflected by an object
  3. Isotherm (b) The lines joining the places of equal temperature
  4. Annual range (a) The difference between the mean temperature of the warmest and the coldest months

Question

The main reason that the Earth experiences highest temperatures in the subtropics in the northern hemisphere rather than at the equator is:

1. Subtropical areas tend to have less cloud cover than equatorial areas.

2. Subtropical areas have longer day hours in the summer than the equatorial.

3. Subtropical areas have an enhanced "green house effect" compared to equatorial areas.

4. Subtropical areas are nearer to the oceanic areas than the equatorial locations.

Solution: The primary reason for higher temperatures in the subtropics compared to the equator is often less cloud cover. While the equator receives more direct solar radiation throughout the year, persistent cloudiness can reduce the amount of insolation reaching the surface. Subtropical regions, particularly during certain seasons, tend to have clearer skies, allowing for greater absorption of solar radiation and thus higher surface temperatures. Longer day hours in summer (option 2) contribute, but less cloud cover is a more consistent factor. The greenhouse effect (option 3) is generally more pronounced at the equator due to higher humidity, and proximity to oceans (option 4) tends to moderate temperatures, not necessarily increase them to subtropical levels.

Question

How does the unequal distribution of heat over the planet Earth in space and time cause variations in weather and climate?

Solution: The unequal distribution of solar radiation across the Earth's surface, both spatially (latitude, land vs. ocean) and temporally (seasons, day vs. night), is the fundamental driver of weather and climate variations. Areas near the equator receive more intense and consistent insolation, leading to higher temperatures, while polar regions receive less direct radiation and are colder. Differences in insolation between continents and oceans, and between summer and winter, create temperature gradients. These temperature differences drive atmospheric circulation, ocean currents, and pressure systems, resulting in diverse weather phenomena like winds, precipitation, and storms, and ultimately shaping the distinct climate zones experienced globally.

Common mistakes

  • Confusing the definitions of insolation and albedo.
  • Incorrectly identifying the latitude where the sun is directly overhead on specific dates.
  • Misunderstanding the primary source of atmospheric heating.
  • Not fully explaining the reasons for temperature differences between equatorial and subtropical regions.

Revision tips

  • Memorize the definitions of key terms like insolation, albedo, and isotherms.
  • Understand the relationship between latitude, angle of incidence, and temperature.
  • Review the factors contributing to the Earth's heat balance.
  • Practice explaining the causes of temperature variations across different regions.

Practice MCQs

Q1. On June 21st, at noon, the sun is directly overhead at which latitude?

Q2. Which of the following cities experiences the longest days?

Q3. What is the primary source of heat for the Earth's atmosphere?

Q4. What does 'Albedo' refer to?

Q5. What is an 'Isotherm'?

Frequently asked questions

What is the main focus of Chapter 9, 'Solar Radiation, Heat Balance and Temperature'?

This chapter focuses on how solar radiation affects Earth's temperature, the balance of heat received and lost, and the factors causing temperature variations across the globe.

What is insolation?

Insolation is the incoming solar radiation that reaches the Earth's surface. It is a key factor in determining surface temperature.

How does albedo affect Earth's temperature?

Albedo is the reflectivity of a surface. Surfaces with high albedo (like snow) reflect more solar radiation, leading to cooler temperatures, while low albedo surfaces (like asphalt) absorb more, leading to warmer temperatures.

Why are temperatures generally higher in subtropical regions than at the equator?

While the equator receives more direct sunlight, subtropical areas often experience less cloud cover and clearer skies, allowing for more solar radiation to reach the surface and contribute to higher temperatures.

What is the difference between insolation and terrestrial radiation in heating the atmosphere?

Insolation (short-wave solar radiation) primarily heats the Earth's surface. The Earth's surface then re-radiates heat as long-wave terrestrial radiation, which is the main process that heats the atmosphere.

How can these NCERT solutions help in exam preparation?

These solutions provide clear, step-by-step answers to the chapter's questions, helping students understand complex concepts, definitions, and geographical reasoning, which is essential for exam success.

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