Important Questions: Solar Radiation, Heat Balance & Temperature | Geography Class 11 - Humanities/Arts PDF Download

Very Short Answer Type Questions

Q1: How much energy radiated by the sun is intercepted by the earth?
Ans: Only A of the billionth fraction of the energy radiated from the sun is intercepted by the earth.

Q2: Where does the energy radiate from the sun come from?
Ans: The energy radiated from the sun comes from nuclear reactions in its core.

Q3: What is the radiant energy of sun commonly known as?
Ans: The radiant energy of the sun is commonly known as short waves or electromagnetic waves.

Q4: What is terrestrial radiation?
Ans: The longwave radiation, i.e., re-emittance of the energy received from the earth’s surface, is terrestrial radiation.

Q5: Define heat budget.
Ans: The gains and losses in heat by incoming and outgoing radiation is known as heat budget.

Q6: What is meant by temperature gradient?
Ans: The rate of change of temperature is called the temperature gradient.

Q7: Define Planck’s law.
Ans: Planck’s law states that hotter a body, the more energy it will ‘ radiate and shorter is the wavelength of that radiation.

Q8: What is insolation?
Ans: The incoming solar radiation is termed as insolation. It comes in the form of short waves.

Short Answer Type Questions

Q9: What are the characteristics of isotherms?
Ans: Main characteristics of isotherms are:

• Isotherms run along the latitudes.
• Isotherms take sudden bends at the land-water edge because of land-water contact.
• They are drawn at equal space which indicates the latitudinal thermal gradient.
• Isotherms change their positions.

Q10: What are the effects of the atmosphere on insolation?
Ans: The energy from the sun passes through different layers of the atmosphere before it reaches the ground. Atmospheric gases are essentially transparent to visible light, but suspended particles of liquid or solid material can absorb or reflect light. A thick cloud may allow less than 10% of sunlight to reach the earth’s surface. Clouds generally behave like mirrors. They reflect sunlight off in different directions rather than absorbing. Reflected sunlight is permanently lost from the earth. The blue colour of the daytime sky is due to the scattering of sunlight.

Q11: Explain why the angle of the sun’s rays falls variably on different latitudes.
Ans: The earth revolves around the sun once in a year in an elliptical path called the ‘plane of ecliptic’. At the same time, the earth rotates on its axis in 24 hours. The earth’s axis is tilted making an angle of 66°30′ from the plane. Due to inclination of the earth’s axis, the angle of the sun’s rays falling on the earth’s surface varies from vertical on the equator to more and more slanting as one moves towards the poles.

Q12: What is the role played by prevailing winds in temperature modification?
Ans: Prevailing winds also affect the temperature conditions of the areas. The moderating effects of oceans are brought to the adjacent lands through winds. On the contrary, off-shore winds take the effects of warm or cold currents away from the land.

Q13: What is global warming? What are its causes?
Ans: The burning of fossil fuels, the cultivation of the soil, industrialisation of land on a large scale, rapid means of transport and deforestation have caused an imbalance in the atmosphere. These activities are increasing the amount of carbon dioxide. Thus, the greenhouse effect has raised the average temperature of the earth by 0,5°C. By the year 2000, the earth’s average temperature will go up by 2°C.

Long Answer Type Questions

Q14: Discuss the impact of altitude on temperature over the atmosphere.
Ans: Altitude is the height of a point above mean sea level, measured vertically. The temperature decreases with increasing height and latitude from the earth’s surface. This vertical decrease in temperature takes place at the rate of 0.65° per 100 metres or 165 metres per 1°C. These variations are normal throughout the troposphere and are termed as normal lapse rate. The atmosphere near the surface is denser and contains a large amount of water vapour and dust particles. Being closer to the land surface, it absorbs more terrestrial heat than that of the upper air. Hence, the temperature is higher in the lower part of the atmosphere than in the upper part, where the air is cleaner. That is why the higher we go, the cooler it is. Ootacamund, Mount Abu, Panchmarhi are cooler in summer than plains.

Q15: How many shapes the sun has? Describe photosphere.
Ans: The sun has three shapes: the core and the interior. The innermost portion of the sun is extremely hot and hence here hydrogen atoms combine to form a smaller number of heavier helium atoms. In this process, certain mass is converted into energy. The Photosphere: Photosphere is the solar surface. The energy produced in the core reaches to this surface. Most of the sun’s energy comes from the photosphere and we see it as a solar disc. In the photosphere, there are granules that transport energy from the base of the photosphere to its surface. Sunspots are dark regions on the photospheres. They are formed due to strong magnetic fields. The energy is released in the form of x-ray and ultra-violet radiations from the sunspots.
Above the photosphere occurs the sun’s atmosphere. The lower part is chromosphere and the upper is the corona. They are visible only during solar eclipses. Corona exudes electromagnetic energy. These energy particles can be captured by earth’s magnetic field in the ionosphere and their interaction with gases produce the aurora.

Q16: What are the basic mechanisms of heat transfer? Discuss the importance of these mechanisms with reference to the atmosphere.
Ans: There are three basic mechanisms of heat transfer:

• Radiation: Radiation is the act of transmitting energy in the form of particles of electromagnetic waves. The process is similar to that of transmission of light from an electric bulb. There are two forms of radiations: solar radiation and terrestrial radiation. The atmosphere gets heated up, in fact, through terrestrial radiation and not by solar radiation.
• Conduction: When two bodies of unequal temperatures are in contact with one another, there is a flow of energy in the form of heat from warmer to cooler body. The layer of air resting upon the warmer earth becomes heated by the process of conduction. The actual conduction during the course of the day affects only the lowest layer of the atmosphere.
• Convection: Convection is the process of heat transfer caused by the dying circulatory movement of the fluid itself. It takes place due to difference in temperature, and hence in density, and the pull of gravity. Convection produces vertical movement. The horizontal movement of a similar nature is called advection.
  

Q17: Isotherms do not show the correct temperature of a place. Discuss.
Ans: Isotherms, which are lines on a map connecting places with the same average temperature, have limitations in accurately representing local temperatures. They provide a general overview but may not capture microclimates, elevation differences, or specific weather events affecting individual places. Factors like proximity to water bodies, altitude, urbanization, and topography can cause significant temperature variations within a short distance. Isotherms also simplify complex temperature data, leading to inaccuracies. Additionally, they represent averages, masking daily or seasonal temperature fluctuations. For precise local temperature information, detailed weather data from localized weather stations is necessary, as isotherms can't account for the intricacies of microclimate conditions impacting specific areas.

Q18: How does the angle of the sun’s rays falling on the ground affect the amount of insolation?
Ans: The angle at which the sun's rays strike the Earth's surface significantly influences the amount of insolation, or incoming solar radiation received at a specific location. When sunlight strikes the Earth directly overhead (at a 90-degree angle), it covers a smaller area, resulting in concentrated energy and higher temperatures. However, as the angle of incidence decreases due to Earth's curvature or seasonal tilt, the same amount of energy is spread over a larger area, leading to lower temperatures. This phenomenon explains the varying intensities of sunlight at different latitudes and during different seasons, contributing to Earth's climate patterns and the changing temperatures experienced across regions.

Q19: What is the difference between direct radiation and diffused radiation?
Ans: Direct radiation and diffused radiation refer to the ways in which solar energy reaches the Earth's surface:

Direct Radiation:

• Definition: Direct radiation, also known as beam radiation, refers to sunlight that travels in a straight line from the Sun to the Earth's surface without being scattered or diffused by the atmosphere.
• Characteristics: Direct radiation delivers concentrated energy to a specific area. It is strongest when the sun is directly overhead (at a 90-degree angle) and provides intense heat and light. Solar panels and solar concentrators are most effective in capturing direct radiation.

Diffused Radiation:

• Definition: Diffused radiation, also called diffuse radiation, is sunlight that has been scattered or reflected by the atmosphere before reaching the Earth's surface. This scattering occurs due to atmospheric particles, clouds, and gases, which redirect the sunlight in various directions.
• Characteristics: Diffused radiation is less concentrated than direct radiation because it is spread out over a larger area. It provides softer, indirect light, often on cloudy or hazy days. Diffused sunlight is still important for plant growth and contributes to daylighting indoors.

In summary, direct radiation is sunlight that reaches the Earth's surface in a straight line without being scattered, while diffused radiation is sunlight that has been scattered or reflected by the atmosphere before reaching the surface. Both types of radiation play roles in various natural and human-made processes, including energy generation, climate patterns, and biological activities.

Q20: Explain how the ocean currents influence the temperature distribution over the earth surface.
Ans: Ocean currents play a crucial role in regulating the Earth's temperature distribution by redistributing heat around the planet. Here's how they influence temperature patterns:

• Heat Redistribution: Ocean currents act like giant conveyor belts, transporting warm water from the equator toward the poles and cold water from the poles toward the equator. Warm ocean currents, such as the Gulf Stream in the North Atlantic, carry tropical heat to higher latitudes, raising temperatures in regions like Western Europe. Cold currents, like the California Current off the western coast of North America, bring colder water from polar regions, cooling the adjacent land areas.
• Moderating Effect: Coastal areas influenced by warm ocean currents experience milder winters and cooler summers. The ocean moderates temperature extremes, leading to a narrower range between the highest and lowest temperatures. This moderating effect is known as maritime influence. Regions near cold currents, on the other hand, might experience cooler temperatures and more significant temperature fluctuations.
• Climate Patterns: Ocean currents influence regional climate patterns. For example, the North Atlantic Drift, an extension of the Gulf Stream, warms the climate of countries like the UK and Norway, making them much milder than other locations at similar latitudes. Similarly, the Kuroshio Current in the Pacific Ocean affects the climate of Japan, making it more temperate than expected for its latitude.
• Precipitation: Ocean currents also influence precipitation patterns. Warm ocean currents evaporate more water into the atmosphere, leading to increased humidity and rainfall in adjacent coastal areas. Conversely, cold ocean currents can reduce evaporation, leading to drier conditions in nearby regions.
• Ecosystems: Ocean currents affect marine ecosystems by transporting nutrients and influencing the distribution of marine life. Upwelling, which occurs when cold, nutrient-rich water rises to the surface, supports vibrant marine ecosystems, as seen off the western coasts of continents where cold currents prevail.