Detailed, Step-by-Step NCERT Solutions for Class 11 Geography Chapter 9 Solar Radiation, Heat Balance and Temperature Questions and Answers were solved by Expert Teachers as per NCERT (CBSE) Book guidelines covering each topic in chapter to ensure complete preparation.
Solar Radiation, Heat Balance and Temperature NCERT Solutions for Class 11 Geography Chapter 9
Solar Radiation, Heat Balance and Temperature Questions and Answers Class 11 Geography Chapter 9
Question 1.
Multiple choice questions :
(i) The sun is directly overhead at noon on June 21 at
(a) The equator
(b) 23.5°S
(c) 23.50°S
(d) 66.5°N
Answer:
(d) 66.5°N.
(ii) In which one of the following cities are days the longest?
(a) Tiruvanantpuram
(b) Chandigarh
(c) Hyderabad
(d) Nagpur
Answer:
(d) Nagpur.
(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 :
| 1. Insolation | (a) The difference between the mean temperature of the warmest and coldest months. |
| 2. Albedo | (b) Lines joining places of equal temperature. |
| 3. Isotherm | (c) Incoming solar radiation. |
| 4. Annual range | (d) The percentage of visible light reflected by an object. |
Answer:
1. (c), 2. (d), 3. (b), 4. (a).
(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 oceanic areas than equatorial locations.
Answer:
(c) Subtropical areas have an enhanced ‘green house effect’ compared to equatorial areas.
Question 2.
Answer the following in about 30 words each :
(i) How does the unequal distribution of heat over the planet earth in space and time cause variations in weather and climate?
Answer:
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.
(ii) What are the factors that control temperature distribution on the surface of the earth?
Answer:
The factors controlling temperature distribution are :
- Latitude
- Altitude
- Land and water
- Prevailing winds
- Ocean currents
(iii) In India, why is the day temperature maximum in May and why not after summer solstice?
Answer:
Because in May, the North Pole is inclined 23’A° toward the sun. As a result, the sun’s rays are vertical at noon over Tropic of Cancer. The sun is always above the horizon throughout the day north of 66!/2°N. So the North polar region experiences six months of sunlight in the summer. The northern hemisphere has longer day hours in summer.
(iv) Why is the annual range of temperature high in the Siberian plains?
Answer:
Annual range of temperature is the difference between the mean temperature of the hottest month and the mean temperature of the coldest month.
It is much pronounced in Siberian plain. The mean January temperature along 60°E longitude is – 20°C both at 80°N and 50°N latitudes. The mean monthly January temperature is over 27°C in equatorial oceans, over 24°C in the tropics, and 2°C to 0° in middle latitudes and -18°C to -48°C in Eurasian continental interior.
Question 3.
Answer the following questions in about 150 words each :
(i) How do the latitude and the tilt in the axis of rotation of the earth affect the amount of radiation received at the surface.
Answer:
The latitude determines the angle of inclination of solar rays. At the equator, the solar rays are nearly vertical and their inclination decreases towards the poles. Between the Tropic of Cancer 23 ‘/2°N and the Tropic of Capricorn (23’/2°S), the solar rays fall vertically twice a year. On any day the inclination of solar rays decreases away from the latitude where the sun is overhead at noon.
Another factor that determines the amount of insolation received at a place is the length of the day. The variation in day length in a year is caused by the tilt of axis of rotation of earth and the revolution of the earth around the sun. The axis of rotation of earth is inclined about 66V20 from the plane of ecliptic.
On March 21st and September 23rd, the sun is overhead at noon over the equator. On these dates the days are 12 hours long all over the world.
On about June 21st, the North pole is inclined 23’A0 towards the sun. As a result, the sun’s rays are vertical at noon over the Tropic of Cancer.
On about December 21st, sun’s rays are vertical over Tropic of Capricorn. The southern hemisphere experiences longer day hours and northern hemisphere experiences shorter day duration.
(ii) Discuss the processes through which the earth atmosphere system maintains heat balance.
Answer:
There are variations in the amount of radiation received at the earth’s surface caused by variation in angle of incidence of sun’s rays, the length of the day and presence of clouds. In the net result, some part of the earth has surplus radiation balance and some other part has deficit radiation balance in the surface atmosphere.
The mean annual temperature of the earth as a whole remains the same. But balance between incoming and outgoing radiation is not uniform and varies from latitude to latitude. In the low latitudes (between 40°N and 40°S) heat gained by shortwave radiation is far more than the heat lost by long wave through the earth’s radiation. While in the higher latitudes, more heat is lost by outgoing long wave than received in short waves.
(iii) Compare the global distribution of temperature in January over the northern and the southern hemisphere of the earth.
Answer:
The global distribution of temperature is generaly shown on the map as isotherms. The deviation from this general trend is more pronounced in January than in July, especially in the northern hemisphere. In the northern hemisphere, the land surface area is much larger than in the southern hemisphere.
Hence, the effects of landmass and the ocean currents are well pronounced. In January the isotherms deviate to the north over the ocean and to south over the continent. The pressure of warm ocean currents, gulf stream and North Atlantic drift make the Northern Atlantic warmer and the isotherms bend towards the north. Temperature decreases over the land and the isotherms bend towards south in Eurasian continent.
