1. The ozone layer is present in:
Correct Answer: d) Stratosphere
Explanation: The ozone layer is located in the lower portion of the stratosphere, approximately 15-35 km above Earth's surface. This layer contains about 90% of atmospheric ozone and absorbs 97-99% of the Sun's harmful ultraviolet radiation.
2. 99% of harmful ultraviolet radiation is prevented by:
Correct Answer: b) Ozonosphere
Explanation: The ozonosphere (ozone layer) absorbs 97-99% of the Sun's medium-frequency ultraviolet light (200-315 nm wavelength). Each ozone molecule absorbs UV radiation and splits into an oxygen molecule and a free oxygen atom, then recombines to repeat the process.
3. 90% of global air pollution is produced by:
Correct Answer: a) Primary air pollutants
Explanation: Primary pollutants (directly emitted) account for ~90% of global air pollution, including particulate matter (PM), carbon monoxide (CO), sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds (VOCs). Secondary pollutants form when primary pollutants react in the atmosphere.
4. A colorless, odorless, and toxic gas produced by incomplete combustion of organic materials is:
Correct Answer: b) Carbon monoxide
Explanation: Carbon monoxide (CO) forms when carbon fuels don't burn completely (vehicles, stoves, furnaces). It binds to hemoglobin 240× more strongly than oxygen, reducing blood's oxygen-carrying capacity. Chronic exposure causes headaches, dizziness, and at high concentrations, death.
5. Sulfur oxides are produced when sulfur-containing fossil fuels are burnt.
Correct Answer: b) Sulfur
Explanation: Sulfur oxides (mainly SO₂) form when sulfur in coal (1-4%) and petroleum burns. SO₂ converts to sulfuric acid (H₂SO₄) in the atmosphere, causing acid rain. Flue-gas desulfurization (scrubbers) can remove 90% of SO₂ from power plant emissions.
6. Inability of the lungs to exchange gases is caused by:
Correct Answer: a) Particulates
Explanation: Particulate matter (PM10, PM2.5) penetrates deep into lungs, causing inflammation and reducing gas exchange efficiency. Chronic exposure leads to COPD, while PM2.5 can enter bloodstream, causing cardiovascular issues. WHO estimates 7 million annual deaths from air pollution.
7. The general term for particles suspended in air is:
Correct Answer: d) Aerosol
Explanation: Aerosols are suspensions of fine solid particles or liquid droplets in air. They range from 0.001 to 100 micrometers and include dust, smoke, sea salt, volcanic ash, and pollution particles. Aerosols affect climate by scattering sunlight and seeding clouds.
8. The geometrical shape of smoke coming out of a chimney is called:
Correct Answer: a) Plume
Explanation: A plume is the visible emission from a point source like a chimney. Its shape depends on atmospheric stability: looping (unstable), coning (neutral), fanning (inversion), or fumigation (pollution reaching ground). Plume behavior helps predict pollution dispersion.
9. The term used to describe a mixture of smoke and fog is:
Correct Answer: d) Smog
Explanation: The term "smog" (smoke + fog) was coined in 1905 to describe London's air pollution. There are two types: (1) Sulfurous smog (London-type) from burning coal, and (2) Photochemical smog (Los Angeles-type) from vehicle emissions reacting in sunlight.
10. Aerosol consisting of water droplets is called:
Correct Answer: c) Fog
Explanation: Fog is a visible aerosol of tiny water droplets suspended near ground level, reducing visibility to <1 km. It forms when air cools to its dew point. Industrial fog often contains pollutants, distinguishing it from natural fog in clean air.
11. Aerosol consisting of solid particles is called:
Correct Answer: a) Smoke
Explanation: Smoke consists of airborne solid and liquid particulates and gases emitted during combustion. Particle sizes range from 0.01 to 1 μm. Wildfire smoke can travel thousands of kilometers, affecting air quality across continents.
12. London smog occurred in the year:
Correct Answer: b) 1952
Explanation: The Great Smog of London (Dec 5-9, 1952) killed 4,000-12,000 people. Cold weather caused residents to burn more coal, while an anticyclone trapped pollution. Visibility dropped to 1 foot, and sulfur dioxide levels reached 7× normal. This led to the Clean Air Act (1956).
13. The white fog accumulated over smoke, turning the city black, forming a ___ smog.
Correct Answer: a) Pea-soup
Explanation: "Pea-soup fog" described London's thick, yellow-black smog, resembling pea soup in color and opacity. It contained soot (carbon particles), sulfur dioxide, and other pollutants from coal burning. Charles Dickens' novels often depicted these fogs.
14. Acid rain is caused by:
Correct Answer: c) SO₂ and NOx
Explanation: Acid rain (pH <5.6) forms when SO₂ and NOx react with water, oxygen, and oxidants to form sulfuric and nitric acids. It damages aquatic ecosystems (pH<5 kills fish), leaches soil nutrients, and corrodes buildings. The 1991 Canada-U.S. Air Quality Agreement reduced emissions.
15. The primary cause of lung cancer due to air pollution is:
Correct Answer: b) Particulate Matter (PM2.5)
Explanation: PM2.5 (particles ≤2.5 μm) penetrates deep into lungs and bloodstream. The WHO classifies outdoor air pollution as Group 1 carcinogen. Long-term exposure increases lung cancer risk by 10-15%. Polycyclic aromatic hydrocarbons (PAHs) in PM are particularly carcinogenic.