The thickness of the ozone column in the atmosphere is measured in which unit?
- A.Dobson unit
- B.Curie
- C.Decibel
- D.Angstrom
Correct answer
Explanation
The correct answer is A, Dobson unit. The Dobson unit, named after the scientist who built the instrument for measuring atmospheric ozone, expresses how thick the ozone column would be if all of it were brought down to the surface at standard temperature and pressure; a hundred Dobson units correspond to a layer one millimetre thick. Option B is wrong because the curie is a unit of radioactivity, used for the rate at which a substance decays. Option C is wrong because the decibel measures the loudness of sound and is used in noise pollution standards. Option D is wrong because the angstrom is a unit of length equal to one ten billionth of a metre, used for atoms and for wavelengths of light rather than for a column of gas. Remember the Dobson unit together with the year 1985, when the thinning over Antarctica was reported.
Read the full article: Ozone Layer and Acid Rain: Causes, Effects, Treaties
Practice Questions
View allWhich of the following statements about ozone is true?
- A.All of the options
- B.Ozone is highly reactive
- C.Ozone protects us from the harmful UV radiation of the sun
- D.Ozone is the major constituent of photochemical smog
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Each of the other three statements is correct on its own, which is exactly why the combined option is the answer.
Read the full explanation →Which of the following is a secondary pollutant?
- A.Carbon monoxide
- B.Smog
- C.Carbon dioxide
- D.Fly ash
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A primary pollutant is released directly from a source, while a secondary pollutant is formed in the atmosphere when primary pollutants react.
Read the full explanation →Which one of the following is NOT a greenhouse gas found naturally in the atmosphere?
- A.Nitrogen oxide
- B.Carbon dioxide
- C.Methane
- D.Ozone
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Nitric oxide and nitrogen dioxide, together written as nitrogen oxides, are air pollutants that come mainly from combustion in vehicles and power stations; they help form smog and acid rain but are not counted among the greenhouse gases of the natural atmosphere.
Read the full explanation →The ozone layer that protects the earth from ultraviolet radiation lies in which layer of the atmosphere?
- A.Troposphere
- B.Stratosphere
- C.Mesosphere
- D.Thermosphere
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About nine tenths of the atmosphere's ozone lies in the stratosphere, roughly fifteen to thirty five kilometres above the surface, where ultraviolet rays split oxygen molecules and the free atoms combine with other oxygen molecules to make ozone.
Read the full explanation →The Montreal Protocol, adopted in 1987, deals with which of the following?
- A.Reduction of greenhouse gas emissions
- B.Substances that deplete the ozone layer
- C.Transboundary movement of hazardous waste
- D.Conservation of wetlands
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The Montreal Protocol was adopted in 1987 under the Vienna Convention of 1985 and sets the timetable by which countries must stop producing and using chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform and methyl bromide.
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