Q2 Physical Geography 1 Mar
Composition And Structure of Atmosphere
1. Most of the weather phenomena takes place in troposphere only because:
(A) Temperature remains almost constant in troposphere.
(B) It contains electrically charged particles.
(C) It absorbs harmful ultraviolet radiation from the sun.
(D) It contains almost all the water vapour and most dust particles.
Ans. (D)
Exp: -The troposphere is the lowest layer of Earth's atmosphere with altitudinal extent of upto 10km. About 75-80% of the mass atmosphere is in the troposphere. Almost all weather phenomenon occurs within this layer. Nearly all of the water vapour and dust particles in the atmosphere are in the troposphere. That is why most clouds are found in this lowest layer. Most of the local, global, seasonal, perennial wind and jet streams circulation happens in troposphere. These in combination to topographical variabilities (mountains, land, sea etc.) give rise to different weather phenomenon. However as the troposphere is heated from below, sunlight warms the ground or ocean, which in turn radiates the heat into the air right above it and thus change in weather pattern with altitude.
2. The combustion of coal and oil is a major source of which greenhouse gas?
(A) Sulphur dioxide
(B) Methane
(C) CFCS
(D) None of the above
Ans. (B)
Exp:- Combustion of fossil fuels like coal and oil release vast majority of greenhouse gases like Carbon dioxide (CO₂), Methane(CH) and Nitrous oxide (N₂O).
Carbondioxide (CO₂) accounts for around three-fourth of the warming impact of current human greenhouse-gas emissions. The key source of C*O_{0} is the burning of fossil fuels such as coal, oil and gas.
Deforestation is also a very significant contributor.
Methane (CH) accounts for 14% of the impact of current human greenhouse-gas emissions. Key sources include agriculture (especially livestock and rice fields), fossil fuel extraction and the decay of organic waste in landfill sites. Methane doesn't persist in the atmosphere as long as C*O_{2} though its warming effect is much more potent for each gram of gas released.
Nitrous oxide (N₂O) accounts for around 8% of the warming impact of current human greenhouse-gas emissions. Key sources include agriculture (especially nitrogen-fertilised soils and livestock waste) and industrial processes. Nitrous oxide is even more potent per gram than methane.
3. Consider the following statements:-
Assertion [A]: Carbon dioxide is an important greenhouse gas.
Reason (R): The human activities increased its concentration in the atmosphere and strengthned the greenhouse effect and has definitely contributed to global warming over the last 100 years.
Select the correct answer from the given options:-
(A) [A] and [R] are correct and [R] is the correct explanation of [A].
(B) [A] and [R] are correct but [R] is not the correct explanation of [A].
(C) [A] is true but [R] is false.
(D) [A] is false but [R] is true.
Ans.(B)
Exp:- Greenhouse Gases like carbon dioxide, methane, nitrous oxides are transparent to incoming solar radiation. These gases do absorb infrared radiation and preventing it from escaping into outer space. The net effect is the gradual heating of Earth's atmosphere and surface, a process known as global Ewarming. The concentration and environment has been rapidly changed by the anthropogenic emissions and has increased the amount of carbon dioxide in atmosphere and subsequent greenhouse gas effect.
However answer is option B as CO2 is a greenhouse gas independent of increase in its concentration due to human activities.
4. Television signal can not be recieved generally beyond a particular distance due to-
(A) Curvature of the earth
(B) Weakness of antenna
(C) Weakness of signal
(D) Absorption of signal in air
Ans.(A)
Exp:- Propagation of radio and television signal happens using part of the VHF (Very High Frequency) spectrum. Radio that is in the VHF band travels in a straight line. In other words, the rays travel using line of sight
However if two users on the opposite side of the world want to communicate, the radio wave cannot use line of sight propagation, because it travels in a straight line and will not go around the curve of the earth. To tackle this satellite and skywave communication is used.
5. Which of the follwoing statement(s) regarding ozone layer within the atmosphere is/are correct?
1. It absorbs most of the ultraviolet radiation found in the Sun's ray.
2. Chlorofluorocarbons are serious threat to the ozone layer.
Select the correct answer using the codes given below:-
Codes:-
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
Ans. (C)
Exp:- The ozone layer acts as a filter for the short wavelength and highly hazardous ultraviolet radiation (UVR) from the sun, protecting life on Earth from its potentially harmful effects. UV radiation capable of penetrating is divided into three categories, based on its wavelength; these are referred to as UV-A (400-315 nm), UV-B (315- 280 nm), and UV-C (280-100 nm).
UV-C, which is very harmful to all living things, is entirely screened out by ozone. UV-B radiation can be harmful to the skin and is the main cause of sunburn; excessive exposure can also cause cataracts, immune system suppression, and genetic damage, resulting in problems such as skin cancer. The ozone layer absorbs about 200 nm to 310 nm with a maximum absorption at about 250 nm. Some UV-B, particularly at its longest wavelengths, reaches the surface, and is important for the skin's production of vitamin D.
Ozone is transparent to most UV-A, so most of this longer-wavelength UV radiation reaches the surface, and it constitutes most of the UV reaching the Earth. This is the least harmful among UV radiation.
The decrease in ozone concentration in the middle layers of the atmosphere - mainly in the stratosphere - is largely caused by anthropogenic emissions of halogenated hydrocarbons, CFCS, HCFCs, halons, carbon tetrachloride and methyl bromide.
6. Consider the following statements:-
Assertion [A]: The composition of the lowest layer of the atmosphere remains relatively constant. Reason [R]: There is intensive mixing and circulation in the lower layers of the atmosphere.
Select the correct answer from the given options:-
(A) Both [A] and [R] are true and [R] is the correct explanation of [A].
(B) Both [A] and [R] are true but [R] is not the correct explanation of [A].
(C) [A] is true but [R] is false.
(D) [A] is false but [R] is true.
Ans. (A)
Exp: The lower layer, up to an altitude of about 80 km above sea level is the homosphere, where due to the continuous turbulent mixing the composition of the atmosphere is relatively constant for chemical species which have long mean residence times.
This region is closed by a thin transition layer, called turbopause. Above the turbopause, in the heterosphere, the molecular diffusion dominates and the chemical composition of the atmosphere becomes stratified and varies according to the molecular mass of chemical compounds.
7. Consider the following statements:-
Assertion [A]: Within the Mesosphere, temperature decreases with increased altitude.
Reason [R]: This is due to decreased solar heating and incresed cooling by CO, radiative emission.
Select the correct answer from the given options:-
(A) Both [A] and [R] are true, and (R) is the correct explanation of [A].
(B) Both [A] and [R] are true, but [R] is not correct explanation of [A].
(C) [A] is true, but [R] is false.
(D) [A] is false, but [R] is true.
Ans.(A)
Exp:- Temperature decreases with increase in altitude in mesosphere and reaches - 100 deg * C at Mesopause (80km above the surface). The atmosphere in a major sense gets heated from the bottom (from the surface). Direct heating from sun is rather low relative to surface heating. Since mesosphere is at very high altitude this heating is rather very low. Also Mesosphere has a lot of radiative cooling. The CO₂ gas present here emits a lot of thermal radiation into space. The energy for this radiative release is obtained by the energy transfer from other molecules at lower levels. Due to lesser density, the radiative cooling is large enough to cause a steep decrease in temperature.
8. Which one of the following layers of the atmosphere is responsible for deflection of radio waves?
(A) Troposphere
(B) Mesosphere
(C) Stratosphere
(D) Ionosphere
Ans.(D)
Exp:-The ionosphere extends upward from 50 km to a height of about 400km. It contains layers of electrically charged ions, which enable radio waves to be propagated to great distances around the Earth. This is the most important region of the atmosphere for long distance point-to-point communications. It uses the principle of SKY WAVES transmission.
Skywaves are radio waves that are reflected back to Earth from the ionosphere.
9. Consider the following statements:-
Assertion [A]: The amount of moisture in the atmosphere is related to latitude.
Reason [R]: The capacity to hold moisture in the form of water vapour is related to temperature.
Select the correct answer from the given options:-
(A) Both [A] and [R] are individually true and [R] is the correct explanation of [A]
(B) Both [A] and [R] are individually true, but [R] is not the correct explanation of [A]
(C) [A] is true, but [R] is false
(D) [A] is false, but [R] is true
Ans.(A)
Exp:- Water vapour capacity increases with increasein temperature. When moisture cools and reaches saturation point, the tiny particles of water condenses into large drops of water (condensation process). There is direct relation between latitude and temperature.Temperature decreases with increase in latitude. Therefore moisture holding capacity of air column decreases with increase in latitude. However fluctuations due to local conditions may be possible.
10. Consider the following statements:
Assertion [A]: The thickness of the atmosphere is maximum over the Equator.
Reason [R]: High insolation and strong convection currents occur over the Equator.
Select the correct answer from the given codes given below:-
Codes:-
(A) Both [A] and [R] are individually true and [R] is the correct explanation of [A]
(B) Both [A] and [R] are individually true, but [R] is not the correct explanation of [A]
(C) [A] is true, but [R] is false
(D) [A] is false, but [R] is true
Ans.(A)
Exp:- Equatorial regions receives high insolation throughout the year and air warmed by contact with it is expanding and rising. This led to formation of strong convective currents. These strong convective currents cause increase in height of the atmosphere. The average altitude of troposphere (lowest layer of atmosphere) is 18 kms whereas at poles it's 8 kms.
Heat differential on the planet's surface also causes convection currents to flow from the equator to the poles.
11. Consider the following statements:-
1. The albedo of an object determines its visual brightness when viewed with reflected light.
2. The albedo of Mercury is much greater than the albedo of the Earth.
Which of the statement(s) given above is/are correct?
(A) Only 1
(B) Only 2
(C) Both 1 and 2
(D) Neither 1 nor 2
Ans. (C)
Exp:- Albedo is the proportion of the incident light or radiation that is reflected by a surface and determines its visual brightness when viewed with reflected light. Surface albedo is defined as the ratio of irradiance reflected to the irradiance received by a surface. It is dimensionless and measured on a scale from zero (corresponding to a black body that absorbs all incident radiation) to one (corresponding to a body that reflects all incident radiation).
The planets are viewed by reflected sunlight and their brightness depends upon the amount of light received from the sun and their albedo. Mercury receives the maximum amount of sunlight, but its albedo is only 0.1 so it is not as bright as it would be with a higher albedo. Whereas albedo for the Earth is given as 0.37. It means earth reflects back more light incident on it compare to mercury which has more insolation than Earth.
12. Which one of the following reflects back more sunlight as compared to other three?
(A) Sand desert
(B) Paddy crop land
(C) Land covered with fresh snow
(D) Prairie land
Ans. (C)
Exp:-The dark surfaces absorb most of the sunlight fall on it and gets heated, whereas shiny surfaces acts like a mirror and reflects back most of the sunlight that fall on it's surface.Albedo tells how bright/white a surface is. Albedo is as high as 0.8 for snow/ice covered surfaces. Also sand, desert, savanna without much vegetation too has high albedo.
However it is low for forests (0.05-0.1) and oceans (0.04-0.07).
Fresh snow - 0.80 -0.90
Sand desert - 0.40
Paddy crop - 0.30
Prairie 0.25
13. A layer in the Earth's atmosphere called Ionosphere facilitates radio communication. Why?
1. The presence of ozone causes the reflection of radio waves to Earth.
2. Radio waves have a very long wave length.
Which of the statement(s) given above is/are correct?
(A) Only 1
(B) Only 2
(C) Both 1 and 2
(D) neither 1 nor 2
Ans. (B)
Exp:- The ionosphere extends upward from 80 km to a height of about 640 km. It contains layers of electrically charged ions (and not ozone), which enable radio waves to be propagated to great distances around the Earth. Radiowaves are type of electromagnetic radiation ranging from 1 mm to 100 km.
14. The formation of ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole?
(A) Presence of prominent tropospheric turbulence and inflow of chlorofluorocarbons.
(B) Presence of prominent polar front and stratospheric clouds and inflow of chlorofluorocarbons.
(C) Absence of polar front and stratospheric clouds and inflow of methane and chlorofluorocarbons.
(D) Increased temperature at polar region due to global warming.
Ans. (B)
Exp:- Polar Stratospheric Clouds play an important role in ozone destruction, in Arctic and Antarctica regions. These high altitude clouds form only at very low temperatures & help destroying ozone in two ways.They provide a surface which converts benign forms of chlorine into reactive, ozone-destroying forms.They remove nitrogen compounds that moderate the destructive impact of chlorine. In recent years, the atmosphere above the Arctic has been colder than usual, and polar stratospheric clouds have lasted over the spring season. As a result, ozone levels have been decreasing
15. The jet aircrafts fly very easily and smoothly in the stratosphere. What could be the appropriate explanation?
1. There are no clouds or water-vapour in the lower stratosphere.
2. There are no vertical winds in the lower stratosphere.
Which of the statements given above is/are correct?
(A) Only 1
(B) Only 2
(C) Both 1 and 2
(D) neither 1 nor 2
Ans. (C)
Exp:- Stratosphere layer is almost free from clouds and not associated with weather phenomenon. Also the temperature in the tropopause and lower stratosphere is largely constant with increasing altitude and there is no vertical wind in this layer.
These conditions makes the the jet aircrafts fly very easily and smoothly in the lower stratosphere.
16. Normally, the temperature decreases with the increase in height from the Earth's surface, because-
1. The atmosphere can be heated upwards only from the Earth's surface.
2. There is more moisture in the upper atmosphere.
3. The air is less dense in the upper atmosphere.
Select the correct answer using the codes given below:-
(A) Only 1
(B) 1 and 3
(C) 2 and 3
(D) 1,2 and 3
Ans. (B)
Exp: The first statement given in this question is correct. Temperature decrease with height at a lapse rate because the air near the surface is heated due to transfer of heat from the ground surface directly. The heat transfer is poor from lower to upper atmosphere and thus temperature decreases with altitude. However the second statement is obviously incorrect. This is because the water vapour accounts for around 1% of air. It varies greatly in troposphere and decreases rapidly with the altitude. The third statements is correct as atmosphere is extremely rarified in upper atmosphere due to very less pressure and thus less density. This limits the heat holding capacity of upper atmosphere.
17. The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs-
(A) The water vapour of the air and retains its heat
(B) The ultraviolet part of the solar radiation.
(C) All the solar radiations
(D) The infrared part of the solar radiation.
Ans. (D)
Exp:- Greenhouse Gases like carbon dioxide, methane, nitrous oxides are transparent to incoming solar radiation. These gases do absorb infrared radiation and preventing it from escaping into outer space. The net effect is the gradual heating of Earth's atmosphere and surface & this process is known as global warming.
18. Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?
(A) The Earth's magnetic field diverts them towards its poles
(B) Ozone layer around the Earth reflects them back to outer space.
(C) Moisture in the upper layers of atmosphere prevents them from reaching the surface of the Earth.
(D) None of the statements (A), (B) and (C) given above is correct.
Ans.(A)
Exp:- The Earth's magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. The interaction between electrically charged particles and magnetic field results in phenomenon of aurora in poles.
19. Consider the following statements:-
Statement [A]: The atmosphere receives most of heat directly from Sun and indirectly from earth's surface. Reason [R]: On the earth's surface, smaller solar waves converted into longer waves.
Select the correct answer from the given options:-
(A) [A] and [R] are correct and [R] is correct expla- nation of [A]
(B) [A] and [R] are correct but [R] is incorrect expla- nation of [A].
(C) [A] is correct but (R) is incorrect.
(D) [A] is incorrect but [R] is correct.
Ans.(A)
Exp:- The atmosphere receives short wavelength sunlight and same is absorbed by earth. However earth after getting warm, releases long wave terrestrial radiation and contributes in rising temperature of earth surface. As the long wave terrestrial radiation are opaque to the atmosphere, these radiations get trapped and ultimately heat up the earth.
20. Which of following statements is not correct?
(A) Water vapour is highly variable in lower atmosphere.
(B) The maximum temperature is found along the equatorial areas.
(C) Frigid zones are located in both the hemispheres between polar circles and poles.
(D) Jet streams flow at high altitude and influenced the weather conditions on earth surface.
Ans.(B)
Exp:- Temperature of a place is measure of heat created by the interaction of insolation with the atmosphere and earth's surface. The factors like latitude, altitude, distance from sea, oceanic currents, impacts temperature of an area. Considering the impact of all these factor in general the highest temperature isotherm is at 20°N of equator.
21. The highest temperatures on earth are recorded at-
(A) Equator
(B) 10° N Latitude
(C) 20° N Latitude
(D) 25° N Latitude
Ans:(c)
Exp:- There are several factors which influence the temperature of a region. The causes are as follows-
i. Insolation-Heat received by the sun
ii. Transparency of Atmosphere
iii. Land-sea Breezes
iv. Oceanic currents
v. Prevailing winds
vi. Altitude
The mentioned factors have cumulative effect on the temperature of a region. The position of the 20° N latitude witnesses all the mentioned factor abundantly. Hence at the tropics, high average temperature occurs.
22. Clear nights are much colder than cloudy nights-
(A) because of condensation
(B) because of radiation
(C) because of insulation
(D) because of conduction
Ans. (B)
Exp:- Water vapours have a very strong green house effect i.e. they prevent the loss of heat from the earth and keeps earth warm. Cloudy nights means higher water vapour content in atmosphere than the cloudless sky. Thus clouds act like blankets which prevent heat energy loss from atmosphere and cloudless sky means rapid loss of radiation to outer space.
23. Which is the lowest layer of the Atmosphere?
(A) Stratosphere
(B) Ozonosphere
(C) Ionosphere
(D) Troposphere
Ans.(D)
Exp:- The troposphere is the first layer above the surface and contains half of the Earth's atmosphere. Air in the troposphere is heated up from the ground. The surface of the Earth absorbs energy and heats up faster than the air does. Weather occurs in this layer.