Read the given source and answer the questions that follow : The main sources of noise pollution are various f

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Q. Read the given source and answer the questions that follow : The main sources of noise pollution are various factories, mechanized construction and demolition works, automobiles and aircraft, etc. There may be added periodical but polluting noise from sirens, loudspeakers used in various festivals, programmes associated with community activities. The level of steady noise is measured by sound level expressed in terms of decibels (dB). Of all these sources, the biggest nuisance is the noise produced by traffic, because its intensity and nature depend upon factors, such as the type of aircraft, vehicle, train and the condition of road, as well as, that of vehicle (in case of automobiles). In sea traffic, the noise pollution is confined to the harbour due to loading and unloading activities being carried. Industries cause noise pollution but with varying intensity depending upon the type of industry. Noise pollution is location specific and its intensity declines with increase in distance from the source of pollution, i.e. industrial areas, arteries of transportation, airport, etc. Noise pollution is hazardous in many metropolitan and big cities in India. (18.1) Explain the meaning of noise pollution. (18.2) Why is noise pollution hazardous in metropolitan cities in India ? (18.3) “Noise pollution is location specific.” Explain with argument.

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Concept understanding — Air Pollution

Air Pollution: A First Look

Imagine you are sitting in a closed room with a friend who just lit a cigarette. The air starts to feel heavy. Your throat tickles. Your eyes sting. That is air pollution in its most direct form — something unwanted has entered the air you breathe, and your body is telling you it does not like it.

Now step outside. That same idea scales up. The air around us is not empty space — it is a mixture of gases (mostly nitrogen and oxygen) plus tiny particles of dust, pollen, and water vapour. When we burn fuels in factories, vehicles, or homes, we add new substances to this mixture: smoke, soot, invisible gases like carbon monoxide and sulphur dioxide. When these reach a concentration high enough to harm living things or damage the environment, we call it air pollution.

Note

The key shift in thinking: air is not "pure" by default. It always contains some dust and natural gases. Pollution is about too much of the wrong thing in the wrong place.

The Precise Definition

Air pollution is the introduction into the atmosphere of substances — called pollutants — that have harmful effects on human health, other living organisms, or the built environment. These pollutants can be:

Gases (e.g., carbon monoxide, nitrogen dioxide, sulphur dioxide, ozone)
Particulate matter (tiny solid or liquid droplets suspended in air — dust, smoke, soot)
Biological molecules (pollen, mould spores — though these are natural, they become "pollution" when they cause harm)

The key word is harmful. A little bit of smoke from a campfire is not pollution if it disperses quickly. But the same smoke trapped in a valley on a windless day, accumulating hour after hour — that is pollution.

Two Main Sources

Source type	Examples	Why it matters
Natural	Volcanic eruptions, forest fires, dust storms, pollen	Usually short-lived or localised; we cannot control them
Anthropogenic (human-made)	Vehicle exhaust, factory chimneys, burning of coal/wood, agricultural burning	This is where most of our pollution problems come from — and what we can fix

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Noise pollution refers to unwanted sound from various human activities, measured in decibels, which is particularly hazardous in densely populated metropolitan cities due to concentrated sources like traffic and industries, and its intensity diminishes with distance from these specific sources.

Noise pollution fundamentally refers to the presence of excessive or unwanted sound in the environment that can be detrimental. While the source does not offer a single, explicit definition, it describes noise pollution as "polluting noise" and a "nuisance" originating from various human activities. The intensity of this steady noise is quantified by its sound level, expressed in decibels (dB). Essentially, it is sound that disrupts the natural environment and human well-being.

Noise pollution poses a significant hazard in metropolitan and large cities across India due to the high concentration and intensity of its primary sources in these urban environments.

Diverse and Concentrated Sources: Metropolitan cities are hubs of industrial activity, with numerous factories contributing to noise. They also experience extensive mechanized construction and demolition works, which are inherently noisy.
Dominance of Traffic Noise: The source identifies traffic as the "biggest nuisance" among all noise sources. Metropolitan cities are characterized by dense road networks, heavy vehicular traffic (automobiles, trains), and often airports, all of which generate substantial and continuous noise. The intensity and nature of this traffic noise vary based on factors like the type of vehicle or aircraft, and even the condition of roads and vehicles.
Community Activities: Periodical but polluting noise from sirens and loudspeakers used in festivals and community programmes further adds to the overall noise burden in these densely populated areas.

Important

The sheer volume and variety of noise-generating activities concentrated in metropolitan areas contribute to the hazardous levels of noise pollution.

The statement "Noise pollution is location specific" means that the impact and intensity of noise pollution are not uniform across an area but are directly tied to the proximity of its source. The argument supporting this is straightforward: …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2026Set ANNUAL1 markMCQ
$Q. Plant indicator for SO2 pollution is :$
(a) Gladiolus, Eucalyptus
(b) Petunia, Chrysanthemum
(c) Robinia pseudoacacia, Casuarina
(d) Lichens, Rose
›Reveal solutionSolution

Lichens are the textbook bio-indicator of SO2 pollution, making option (d) the correct pairing among the four.

Working

Certain plants and plant-like organisms are used as biological indicators of specific air pollutants because they show visible damage (chlorosis, necrosis, reduced growth, or local disappearance) at pollutant concentrations too low to be obvious by other means. For sulphur dioxide (SO2), the single most widely cited bio-indicator is the lichen -- a symbiotic association of a fungus and an alga/cyanobacterium. Lichens lack a waxy cuticle and absorb gases (including SO2) directly over their whole surface, and their photosynthetic algal partner is especially sensitive to sulphite toxicity; as a result, lichens are killed or fail to establish in areas with even modest SO2 pollution, and the sharp fall in lichen diversity around industrial/urban centres (sometimes called a 'lichen desert') is a classic, long-used indicator of chronic SO2 pollution. Sensitive flowering ornamentals such as rose have also been used in pollution-monitoring gardens as visible SO2-sensitive indicator plants alongside lichens. Checking the oth …

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CBSE 2023Set 64/3/11 markMCQ
$Q. Which one of the following is the cause of acid rain ? (A) Land pollution (B) Water pollution (C) Air pollution (D) Noise pollution$
›Reveal solutionSolution

Acid rain is caused by air pollution, specifically when certain gases released into the atmosphere mix with rainwater.

Acid rain is a direct consequence of air pollution. When we burn fossil fuels — coal, oil, petrol — in factories, power plants, and vehicles, they release gases like sulphur dioxide and nitrogen oxides into the air. These gases rise high into the atmosphere, where they react with water vapour, oxygen, and sunlight. This chemical reaction turns them into sulphuric acid and nitric acid. When it rains, these acids come down with the raindrops, making the rain acidic — hence the name "acid rain."

Note

Normal rain is already slightly acidic because carbon dioxide in the air dissolves in it to form weak carbonic acid. But acid rain is far more acidic, with a pH below 5.6, and that extra acidity comes from human-made air pollutants.

So the root cause is not something on the ground like garbage or sewage. Land pollution (A) involves solid waste and chemicals dumped on soil, but those don't rise into the sky to form acid rain. Water pollution (B) is about contaminants in rivers, lakes, and oceans — again, not airborne. Noise pollution (D) is about sound, which has nothing to do with chemistry in the clouds. …
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CBSE 2023Set ANNUAL1 mark
$Q. Which device is used to clean both dust and gases from polluted air?$
›Reveal solutionSolution

A scrubber is an air-pollution control device that removes both particulate matter (dust) and gaseous pollutants from industrial exhaust before it is released.

A scrubber works by passing polluted exhaust gas through a spray or bed of a scrubbing liquid (often water or an alkaline solution). Fine dust and particulate matter are trapped/washed out by the liquid droplets, while acidic or other soluble gaseous pollutants (such as SO2) are absorbed and neutralised by chemical reaction with the scrubbing liqu …

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CBSE 2019Set 64/2/11 mark
$Q. How does air pollution affect human health ?$
(OR)
$How does noise pollution affect human health ?$
›Reveal solutionSolution

Part (a): Air pollution causes respiratory diseases (asthma, bronchitis, lung cancer) and heart problems, plus eye and throat irritation.

Part (b): Noise pollution causes hearing loss and deafness and raises stress, disturbing sleep and causing high blood pressure and poor concentration.

Part (a)

Air pollution affects human health mainly by being breathed in. The respiratory system is hit first: polluted air irritates and inflames the airways, causing coughing, wheezing and breathlessness, and it triggers or worsens asthma, bronchitis and chronic lung diseases. Fine particulate matter (PM2.5) is especially dangerous because it penetrates deep into the lungs, and long-term exposure raises the risk of lung cancer. The cardiovascular system is also affected — fine particles entering the bloodstream cause inflammation, hardening of the arteries and higher blood pressure, increasing the risk of heart attacks and strokes, while carbon monoxide reduces the blood's oxygen-carrying capacity. In addition, pollutants cause eye and throat irritation, headaches and fatigue. Children, the elderly and people with existing heart or lung conditions suffer the most.

Part (b) …
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CBSE 2018Set ANNUAL1 markMCQ
$Q. Photochemical smog contains$
(a) PAN
(b) Ozone
(d) Nitrogen dioxide
(e) All of the above
›Reveal solutionSolution
Photochemical smog is a mixture of secondary pollutants — PAN, ozone, and NO2 — formed by sunlight-driven reactions of primary pollutants.

Note on scope: this question tests air-pollution chemistry (photochemical smog), part of the 'Environmental Issues' unit. That specific unit is not part of the current rationalised NCERT syllabus this platform's chapter content is built from, so a chapter-linked lesson isn't available here — but the question itself has a clear, well-established answer, given below.

Photochemical smog forms when primary pollutants from vehicle/industrial exhaust — nitrogen oxides and unburnt hydrocarbons — react with each other in the presence of sunlight (UV radiation), producing a cocktail of secondary pollutants. Its major components include:

PAN (peroxyacetyl nitrate) — a strong eye and respiratory irritant. …
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CBSE 2016Set ANNUAL1 mark
$Q. Why PUC is mandatory for all vehicles?$
›Reveal solutionSolution

PUC checks keep vehicle emissions within legal limits, curbing air pollution and its health effects.

Vehicles burning petrol or diesel release polluting gases such as carbon monoxide, unburnt hydrocarbons, oxides of nitrogen, and particulate matter, all of which degrade air quality and contribute to respiratory diseases, smog formation and global warming. A PUC (Pollution Under Control) certificate is issued only after a vehicle's exhaust emissions are tested and found to be within government-prescribed limits. Making this mandatory for all vehicles ensures that poorly maintained or high-polluting vehicles are identified, repaired or taken off the road, thereby reducing the overall vehicular contribution to urban air pollution, safeguarding public he …

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