NCERT Class 11 Geography Chapter 8: SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE | Line-by-Line MCQs & Mains Questions for UPSC

Chapter Insights: Chapter -8- SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

📚 NCERT Integrated 📖 Standard Book Ref ✅ PSC & UPSC Aligned

This chapter explores the fundamental concepts of solar radiation, the heat balance of the Earth-atmosphere system, and the resulting temperature distribution. It begins with insolation (incoming solar radiation), explaining its variability due to Earth's rotation, axial tilt, and orbital position (aphelion and perihelion).

The spatial distribution of insolation is highest over subtropical deserts and decreases towards the poles. The chapter then details the mechanisms of atmospheric heating and cooling: conduction, convection, advection, and most importantly, terrestrial radiation—the long-wave radiation from the Earth that heats the atmosphere from below.

This leads to the concept of the Earth's heat budget, a state of balance where 100 units of incoming solar energy are ultimately reflected or radiated back to space, preventing perpetual warming or cooling. The surplus heat in the tropics is redistributed towards the poles via atmospheric and oceanic circulations.

Finally, the chapter examines the factors controlling temperature distribution: latitude, altitude, distance from the sea, air masses, and ocean currents. It analyses global temperature patterns using isotherms, noting the pronounced effects of continentality and warm ocean currents like the Gulf Stream.

The phenomenon of temperature inversion, where temperature increases with height, is also explained, along with its effects like fog formation and frost protection in valleys.

Note on Coverage: These questions are developed through a line-by-line analysis of the textbook. This ensures that even the smaller details and nuanced concepts often overlooked are covered for comprehensive exam preparation.

Preparation Method

We recommend reading the NCERT chapter thoroughly before attempting these questions. The page numbers provided correspond to the actual textbook pages to help you locate the source material quickly.

Section A: Descriptive Questions

  1. What is insolation? Explain the concept briefly. (Pg. 1) Page 67
  2. What are the main factors that cause variations in insolation at the Earth's surface? (Pg. 1-2) Page 67-68
  3. Describe the spatial distribution of insolation across the Earth's surface. (Pg. 2) Page 68
  4. What is advection and how does it influence weather, especially in middle latitudes? (Pg. 2) Page 68
  5. Explain the heat budget of the Earth. How is the incoming solar energy balanced? (Pg. 3) Page 69
  6. What does Figure 8.3 indicate about the latitudinal variation in net radiation balance? (Pg. 4) Page 70
  7. Explain how distance from the sea moderates temperature. (Pg. 4) Page 70
  8. Describe the major features of global temperature distribution in January. (Pg. 5) Page 71
  9. What is temperature inversion? Describe an ideal condition for it to occur. (Pg. 7) Page 73

Section B1: Multiple Choice Questions

Page 67

When is the earth at its farthest point from the sun (aphelion)? (Pg. 1)

A) January 3rdB) July 4thC) March 21stD) December 22nd
View Answer
Answer: B
Source Reference: Page 67
Page 68

Why do slant sun rays (at higher latitudes) result in less net energy per unit area? (Pg. 2)

A) They pass through less atmosphere.B) They cover a smaller area.C) They are absorbed by clouds only.D) They cover a larger area, distributing energy.
View Answer
Answer: D
Source Reference: Page 68
Page 68

Over which areas is maximum insolation received? (Pg. 2)

A) Polar RegionsB) Subtropical DesertsC) Equatorial RainforestsD) Temperate Grasslands
View Answer
Answer: B
Source Reference: Page 68
Page 68-69

What is the primary process by which the atmosphere is heated from below? (Pg. 2-3)

A) ConductionB) ConvectionC) Terrestrial RadiationD) Advection
View Answer
Answer: C
Source Reference: Page 68-69
Page 69

What is the term for the percentage of solar radiation reflected back by the Earth and its atmosphere? (Pg. 3)

A) AbsorptionB) AlbedoC) ConvectionD) Lapse Rate
View Answer
Answer: B
Source Reference: Page 69
Page 70

Which of the following is NOT a factor controlling the temperature distribution of a place? (Pg. 4)

A) LatitudeB) AltitudeC) Ocean CurrentsD) Earth's Magnetic Field
View Answer
Answer: D
Source Reference: Page 70
Page 70

Why do places at higher altitudes generally have lower temperatures? (Pg. 4)

A) They receive less insolation.B) The atmosphere is heated directly by the sun.C) The atmosphere is heated by terrestrial radiation from below.D) They have more cloud cover.
View Answer
Answer: C
Source Reference: Page 70
Page 71

In January, why do isotherms bend northward over the North Atlantic Ocean? (Pg. 5)

A) Due to continentalityB) Due to warm ocean currents (Gulf Stream)C) Due to high altitudeD) Due to cold air masses
View Answer
Answer: B
Source Reference: Page 71
Page 73

What is a common consequence of a surface temperature inversion? (Pg. 7)

A) Clear skies and high windsB) Formation of dense fog and stable airC) Increased vertical air movementD) Rapid warming of the earth's surface
View Answer
Answer: B
Source Reference: Page 73
Page 73

(Exercise) The sun is directly overhead at noon on 21st June at: (Pg. 7)

A) The equatorB) 23.5° SC) 23.5° ND) 66.5° N
View Answer
Answer: C
Source Reference: Page 73
Page 73

(Exercise) The atmosphere is mainly heated by the: (Pg. 7)

A) Short wave solar radiationB) Reflected solar radiationC) Long wave terrestrial radiationD) Scattered solar radiation
View Answer
Answer: C
Source Reference: Page 73
Page 74

(Exercise) The main reason the earth experiences highest temperatures in the subtropics rather than at the equator is: (Pg. 8)

A) Longer summer daysB) Less cloud cover in subtropicsC) Enhanced greenhouse effectD) Nearness to oceans
View Answer
Answer: B
Source Reference: Page 74

Section B2: One-Word / Factual Check

The energy received by the earth from the sun is termed ______. (Pg. 1) Page 67

Show Answer
insolation (Reference: Page 67)

The red colour of the rising/setting sun and blue sky are results of ______ of light. (Pg. 2) Page 68

Show Answer
scattering (Reference: Page 68)

The transfer of heat through direct contact between two bodies is called ______. (Pg. 2) Page 68

Show Answer
conduction (Reference: Page 68)

The process of vertical heating of the atmosphere through rising air currents is ______. (Pg. 2) Page 68

Show Answer
convection (Reference: Page 68)

Out of 100 units of insolation, roughly ______ units are absorbed by the Earth's surface. (Pg. 3) Page 69

Show Answer
51 (Reference: Page 69)

The rate of decrease of temperature with increasing height is called the ______. (Pg. 4) Page 70

Show Answer
normal lapse rate (Reference: Page 70)

Lines joining places of equal temperature on a map are called ______. (Pg. 5) Page 71

Show Answer
isotherms (Reference: Page 71)

The highest range of temperature (>60°C) is found over the ______ part of Eurasia. (Pg. 7) Page 73

Show Answer
north-eastern (Reference: Page 73)

In hilly areas, cold air flowing down slopes to collect in valleys is called air ______. (Pg. 7) Page 73

Show Answer
drainage (Reference: Page 73)

(Exercise) Pair the term 'Albedo' with its correct definition. (Pg. 8) Page 74

Show Answer
The percentage of visible light reflected (Reference: Page 74)

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