Insolation - Questions & Answers
EXERCISESI. Choose the correct option:
1. The sun continuously radiates heat and light energy in all the directions known as:
(a) Energy radiation
(b) Solar radiation
(c) Sun radiation
(d) Heat and light radiation
Answer: (b) Solar radiation
2. Assertion (A): Heat absorption capacity of air is more in the lower layers than in upper layers.
Reason (R): Air on the surface of the earth is denser and contains more carbon dioxide, water vapour and other gases.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.
3. The solar energy received by the earth is called:
(a) Radiation
(b) Insolation
(c) Greenhouse radiation
(d) Precipitation radiation
Answer: (b) Insolation
4. The heat radiated by the earth in the form of long waves is called:
(a) Terrestrial radiation
(b) Heat balance
(c) Conduction
(d) Convection
Answer: (a) Terrestrial radiation
5. When both incoming radiation and outgoing radiation are balanced, it is called:
(a) Convection
(b) Terrestrial radiation
(c) Heat balance
(d) Conduction
Answer: (c) Heat balance
6. Of the insolation, 35% is reflected by the atmosphere; how much reaches the earth's surface?
(a) 14%
(b) 51%
(c) 35%
(d) 34%
Answer: (b) 51%
7. Conduction : direct contact :: Convection : circulatory motion
(a) direct contact; circulatory motion
(b) circulatory motion, direct contact
(c) absorption, transference
(d) transference, absorption
8. The atmosphere is warmed by 14% of insolation and 34% of terrestrial radiation regulating earth's temperature preventing extremes of temperature.
(a) A : 14; B : 34
(b) A : 35; B : 35
(c) A : 14; B : 48
(d) A : 51; B : 17
9. The height of a place above the mean sea level:
(a) Latitude
(b) Altitude
(c) Height
(d) Sea level height
Answer: (b) Altitude
10. Land : conduction :: Water : convection
(a) circulation, convection
(b) currents, breeze
(c) conduction, convection
(d) circulation, circumvention
11. Sea breeze : daytime :: land breeze : night time
(a) daytime
(b) night time
(c) dawn
(d) dusk
12. The increase in temperature in valleys: Inversion of temperature
(a) Mountain breeze
(b) Normal lapse rate
(c) Inversion of temperature
(d) Valley breeze
II. Short Answer Questions
1. What is solar radiation? What is its significance for the earth?
Answer: Solar radiation is the continuous flow of heat and light energy radiated by the sun in all directions. Its significance is that it is the primary and only source of light and heat for the earth, providing the energy needed for all movement, processes, and changes on our planet.
2. What is meant by insolation? State two of its main characteristics.
Answer: Insolation is the specific amount of solar energy that is received by the earth. Two main characteristics are: (i) It travels and reaches the earth in the form of short wave rays. (ii) Only a tiny fraction (one part out of two billion parts) of the sun's total radiated energy actually reaches the earth.
3. State two advantages of convectional heating of the atmosphere.
Answer: Two advantages are: (i) Convection currents cause the movement of air that produces phenomena like sea breezes, which help cool and moderate coastal regions. (ii) It helps in the continuous transfer and distribution of heat from one medium to another (or from one level to another) through circulatory movements in the atmosphere and oceans.
4. Name four factors that affect the temperature of a place.
Answer: Four factors are: Latitude, altitude, distance from the sea, and slope of the land (winds and ocean currents also heavily affect temperature).
5. State the pattern of temperature in mid latitudes.
Answer: In the mid-latitudes (the Temperate Zones), the sun's rays strike the earth at a slanting or oblique angle. Because slanting rays travel a longer distance through the atmosphere and spread their heat over a larger surface area, they have less heating power, resulting in moderate or lower temperatures compared to the Tropics.
6. What difference is there in the temperatures on a mountain and on a sea shore?
Answer: The temperature on a mountain is generally much cooler due to high altitude, as temperature naturally decreases at a rate of 6°C per kilometer of ascent (Normal Lapse Rate). Conversely, on a seashore at sea level, the temperature is typically warmer but remains highly moderated and equable due to the continuous interchange of land and sea breezes.
7. Why is India cooler in December than in July?
Answer: Owing to the inclination of the earth on its axis and its annual revolution, India receives highly slanting (oblique) rays of the sun in December. These slanting rays must travel a longer distance and spread over a wider area, thus losing heating power. In July, the rays are much more vertical and concentrated, leading to hotter temperatures.
III. Distinguish between each of the following:
1. Insolation and Terrestrial Radiation.
Answer: Insolation is the incoming solar energy received by the earth from the sun, which travels in the form of short waves. Terrestrial Radiation is the heat that the earth's surface radiates back into the atmosphere in the form of long waves after it has been absorbed.
2. Land breeze and sea breeze.
Answer: A land breeze is the cool breeze that blows from the cooler land towards the relatively warmer sea during the night. A sea breeze is the cool breeze that blows from the cooler sea towards the warmer, low-pressure land area during the daytime.
IV. Structured Questions
1. (a) How is 'heat balance' achieved?
Answer: Heat balance is achieved by a state of equilibrium where the incoming insolation from the sun matches the outgoing terrestrial radiation from the earth. The atmosphere helps maintain this by reflecting 35% of incoming energy, absorbing 14% of it, and absorbing 34 units of the earth's outgoing terrestrial radiation, preventing extreme temperature changes between day and night.
1. (b) State how latitude affects the temperature of a place.
Answer: Temperature gradually decreases with an increase in latitude on either side of the Equator. This is because the earth is spherical, so near the Equator, the sun's rays strike almost vertically, concentrating intense heat over a smaller area. At higher latitudes, the rays become slanting, traveling further through the atmosphere and spreading over a larger area, heavily reducing their heating power.
1. (c) Give a reason for each of the following:
(i) North India has a greater range of temperature than South India.
Answer: North India lies in the continental interior, far from the ocean. Land heats and cools very rapidly, leading to a massive temperature contrast and great range. South India is coastal, so the sea's water continuously moderates the temperature via land and sea breezes, creating a lower temperature range.
(ii) The temperature of Delhi is less than that of Chennai in December.
Answer: Delhi is located at a much higher latitude than Chennai. Because temperature decreases as latitude increases due to the sun's rays becoming more slanting and losing heating power, Delhi remains much colder than Chennai during December.
(iii) Desert areas experience a high day temperature and a much lower night temperature.
Answer: Desert landmasses get heated and cooled extremely fast. During the day, the land heavily absorbs direct insolation, causing high heat. At night, without moisture or thick cloud cover to trap it, the heat from the surface rapidly escapes back into space as terrestrial radiation, plunging the temperature very low.
1. (d) Draw a well labelled diagram to show the Heat Budget of the earth.
Answer: [Students should draw a diagram demonstrating 100% incoming solar radiation, showing 35% reflected back into space, 14% absorbed by the atmosphere, and 51% reaching the earth's surface. It should also show the outgoing terrestrial radiation with 34% absorbed by the atmosphere and 17% escaping directly into space, to show the total balance.]
2. (a) State the five temperature zones of the earth.
Answer: The earth is divided into the Torrid Zone, the North Temperate Zone, the South Temperate Zone, and the two Frigid Zones (North and South).
2. (b) Explain the Normal Lapse Rate.
Answer: The Normal Lapse Rate is the standard rate at which temperature decreases with height, which is about 6°C per kilometer (or 1°C for every 166 metres) above sea level. This occurs because the atmosphere is primarily heated from below by long-wave terrestrial radiation. Lower atmospheric layers are denser and hold more heat-absorbing greenhouse gases than the thinner upper layers.
2. (c) Give a reason for each of the following:
(i) Distance from the sea affects the temperature of a place.
Answer: Water is highly mobile and its warm and cold layers mix easily, meaning it heats up and cools down much slower than land. Coastal areas receive cool sea breezes during the day and warm land breezes at night, completely moderating the daily and annual temperature compared to extreme inland areas.
(ii) Land is heated and cooled faster than the sea.
Answer: The sun's rays heat a solid piece of land very rapidly because the heat remains confined solely to the surface area and does not mix. In contrast, water is mobile, allows the sun's rays to penetrate to a great depth, and actively mixes its warm and cold waters, making it very slow to heat and cool.
(iii) The ports of the western coast of Europe remain ice-free during winter.
Answer: Ocean currents transport massive amounts of heat. The Warm North Atlantic Drift continuously carries warm equatorial water to higher polar latitudes, effectively raising the ambient winter temperature of North-West Europe and preventing its ports from freezing over.
2. (d) Draw a well labelled diagram showing that the vertical rays are hotter than slanting rays.
Answer: [Students should draw a diagram showing vertical rays covering a smaller, concentrated surface area (resulting in more heat), and slanting rays travelling further and spreading out to cover a much wider, less heated area.]
3. (a) How does the distance from the sea affect the distribution of temperature?
Answer: Areas positioned close to the sea have much lower daily and annual ranges of temperature, enjoying a stable, moderate climate due to the interchange of sea and land breezes. Conversely, places situated deep in the continental interior experience massive temperature contrasts and very extreme weather.
3. (b) How would the breezes that blow during the day and those that blow during the night affect the temperature of a place situated in the coastal region?
Answer: During the day, the cool sea breeze forcefully blows inland, significantly lowering the hot daytime temperature of the land. At night, the land breeze blows outwards from the rapidly cooling land towards the warmer sea. This continuous daily interchange perfectly maintains the heat balance and ensures a moderate coastal climate.
3. (c) Give a reason for each of the following:
(i) Higher the latitude, lower is the temperature.
Answer: Due to the earth's spherical shape, the higher the latitude, the more slanting the sun's angle of incidence becomes. Slanting rays have to travel a much longer distance through the atmosphere and spread their energy over a much wider area, drastically reducing their heating power.
(ii) The vertical rays of the sun give more insolation than the slanting rays.
Answer: Vertical rays travel a much shorter, direct distance through the atmosphere and fiercely concentrate all their heat onto a smaller specific area, resulting in intense insolation and higher temperatures.
(iii) A desert region has a high range of temperature than a forest region.
Answer: Dry desert landmasses heat up aggressively under the sun and cool off completely at night, creating an extreme daily range. A forest region retains high moisture levels and water vapor which act similarly to the sea, slowly absorbing and releasing heat, effectively moderating the temperature range.
3. (d) Draw a well labelled diagram to show the land and sea breeze.
Answer: [Students should draw two diagrams: One showing a daytime cool sea breeze blowing from the high-pressure ocean to the low-pressure warm land, and one showing a nighttime warm land breeze blowing from the high-pressure cold land to the low-pressure warmer ocean.]
V. Thinking Skills
1. Solar radiation is the only primary source of light and heat on the earth. But only 51% of solar energy reaches the earth. What would happen if the entire solar energy reaches the earth? Give reasons to support your answer.
Answer: If 100% of the entire solar energy reached the surface without the atmosphere's protection, the earth's delicate heat balance would be permanently destroyed. The earth's surface would become intensely and dangerously hot during the day because 35% of the energy normally reflected back into space and 14% absorbed by the upper atmosphere would constantly bombard the surface, creating lethal temperature extremes that would make it impossible for any life to survive.
2. Do you think Greenhouse Gases affect earth's heat budget? Give examples to support your answer.
Answer: Yes, greenhouse gases profoundly affect the earth's heat budget. Gases like carbon dioxide and water vapour are highly dense in the lower atmosphere and possess a massive heat-absorption capacity. During the night, they actively absorb the 34 units of long-wave terrestrial radiation given out by the earth. Without these gases trapping the heat like a glass greenhouse, all warmth would rapidly escape into space, causing the earth to become lethally freezing cold every single night.