NCERT Solutions Class-11 Geography Chapter-8: Solar Radiation, Heat Balance and Temperature
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NCERT Solutions Class-11 Geography Chapter-8: Solar Radiation, Heat Balance, and Temperature
Exercises Page No: 78
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
Answer:
(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
Answer:
(a) Tiruvanantpuram
(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
Answer:
(c) Long wave terrestrial radiation
(iv) Make correct pairs from the following two columns.
|
(i) Insolation |
(a) The difference between the mean temperature of the warmest and the coldest months |
|---|---|
|
(ii) Albedo |
(b) The lines joining the places of equal temperature |
|
(iii) Isotherm |
(c) The incoming solar radiation |
|
(iv) Annual range |
(d) The percentage of visible light reflected by an object |
Answer:
|
(i) Insolation |
(c) The incoming solar radiation |
|---|---|
|
(ii) Albedo |
(d) The percentage of visible light reflected by an object |
|
(iii) Isotherm |
(b) The lines joining the places of equal temperature |
|
(iv) Annual range |
(a) The difference between the mean temperature of the warmest and the coldest months |
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.
Answer:
(b) Subtropical areas have longer day hours in the summer than the equatorial.
Que 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?
Answer:
The sun provides energy to the Earth, which then radiates some of it back into space. This balance maintains the Earth’s temperature overall. However, different parts of the Earth receive varying amounts of heat, creating pressure differences in the atmosphere. Winds then transfer this heat from one region to another, affecting weather and climate. This unequal distribution of heat across the Earth’s surface leads to changes in weather patterns and long-term climate variations.
(ii) What are the factors that control temperature distribution on the surface of the earth?
Answer:
Factors controlling temperature distribution include latitude, altitude, distance from the sea, air mass circulation, and ocean currents.
(iii) In India, why is the day temperature maximum in May and why not after the summer solstice?
Answer:
In India, the day temperature peaks in May due to the summer solstice, when the sun’s rays are directly overhead the Tropic of Cancer, before the monsoon brings cooling.
(iv) Why is the annual range of temperature high in the Siberian plains?
Answer:
The high annual temperature range in the Siberian plains is due to the extreme cold winters, with January temperatures averaging around -20°C between 80°N and 50°N, while July temperatures rise above 10°C, creating a substantial difference in temperature throughout the year.
Que 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?
Answer:
The amount of sunlight received on Earth varies due to the angle at which the sun’s rays hit the surface, influenced by latitude. Higher latitudes receive sunlight at a slant, covering less area and resulting in less energy per unit area. Moreover, slanting rays pass through more atmosphere, leading to absorption, scattering, and diffusion, reducing the net energy received. Sun rays are vertical at the equator year-round. As the sun’s position changes from 0° to 23.5° north and south, its rays fall vertically on the Tropic of Cancer from March 1st to 21st, and on the Tropic of Capricorn from September 23rd to 22nd. Towards the poles, temperatures decrease. Beyond 66.5°N and S, a cold zone exists because slanting sun rays result in lower temperatures throughout the year. The tilt of Earth’s axis affects the radiation received at the surface.
(ii) Discuss the processes through which the earth-atmosphere system maintains heat balance.
Answer:
The energy from the Sun reaches the Earth through radiation and circulates through various processes. The Earth maintains its temperature by balancing the heat received from the Sun with the heat lost through terrestrial radiation.
- While passing through the atmosphere, some solar energy is reflected, scattered, and absorbed. Roughly 35 units are reflected back to space before reaching the Earth’s surface. Of these, 27 units are reflected from clouds and 2 units from snow and ice-covered areas.
- The remaining 65 units are absorbed, with 14 units absorbed within the atmosphere and 51 units by the Earth’s surface. The Earth then radiates back 51 units as terrestrial radiation.
- Of these, 17 units are radiated directly into space, and the remaining 34 units are absorbed by the atmosphere.
- The total radiation returning from the Earth and the atmosphere, respectively, is 17 + 48 = 65 units, balancing the total of 65 units received from the Sun. This equilibrium is known as the heat budget or heat balance of the Earth, ensuring it neither warms up nor cools down significantly.
(iii) Compare the global distribution of temperature in January over the northern and the southern hemisphere of the earth.
Answer:
The distribution of isotherms, which are lines connecting places with the same temperature, is influenced by various factors such as landmasses and ocean currents. In the Northern Hemisphere, where landmasses dominate, isotherms deviate northward over the ocean due to warm ocean currents like the Gulf Stream and North Atlantic Drift. Conversely, over continents, isotherms bend southward due to sharp temperature decreases. This is evident in regions like the North Atlantic Ocean and Europe.
In the Southern Hemisphere, where oceanic influences are stronger, isotherms generally run parallel to latitudes. The variation in temperature is more gradual compared to the Northern Hemisphere. For instance, isotherms of 20°C, 10°C, and 0°C run parallel to latitudes 35°S, 45°S, and 60°S respectively. This demonstrates how oceanic factors contribute to a more uniform temperature distribution in the Southern Hemisphere.
NCERT Solutions Class 11 Geography Chapter 8: Solar Radiation, Heat Balance and Temperature Summary
Chapter 8 of Class 11 Geography teaches us about how the sun’s energy affects the Earth’s climate and temperature.
Sun’s Energy: The sun provides energy to the Earth, but it’s not spread out evenly. Some places get more sunlight than others because of factors like the angle of the sun and what’s in the atmosphere.
Balancing Heat: Even though the Earth gets a lot of heat from the sun, it doesn’t get too hot because it also gives off heat. This balance keeps the Earth’s temperature stable over time.
Factors Affecting Temperature: Different things like where you are on Earth, how high up you are, and how close you are to the ocean affect how hot or cold it is. These factors create different climate zones around the world.
Temperature Patterns: We can map out temperature patterns using lines called isotherms. These lines connect places with the same temperature. Land and ocean currents play a big role in deciding where these lines go.
Strange Temperature Changes: Sometimes, the temperature doesn’t follow the usual patterns. Events like El Nino or La Niña can cause big changes in temperature, which can affect weather around the world.
FAQs on NCERT Solutions Class 11 Geography Chapter 8: Solar Radiation, Heat Balance and Temperature
What is solar radiation?
Solar radiation is the energy emitted by the sun in the form of electromagnetic waves. It is responsible for heating the Earth’s surface and driving weather patterns.
How does the Earth maintain its temperature?
The Earth maintains its temperature through a balance of incoming solar radiation and outgoing terrestrial radiation. This balance keeps the Earth’s temperature relatively stable over time.
What factors affect temperature distribution on Earth?
Temperature distribution on Earth is influenced by factors such as latitude, altitude, proximity to large bodies of water, ocean currents, and atmospheric circulation patterns.
What are isotherms?
Isotherms are lines on a map that connect points of equal temperature. They help visualize temperature patterns across regions and continents.
How do El Nino and La Nina affect global temperatures?
El Nino and La Nina are climate phenomena caused by changes in ocean temperatures in the Pacific Ocean. El Nino leads to warmer-than-average sea surface temperatures, while La Nina leads to cooler-than-average temperatures. These events can disrupt global weather patterns and impact temperature distribution.