Air Pollution Practice Questions
20 free Air Pollution practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is the most widely used method to remove particulate matter from the exhaust of a thermal power plant?
- A Catalytic converter fitted in exhaust pipe
- B Electrostatic precipitator
- C Wet scrubber in chimney stack
- D High-temperature incinerator
Correct answer: Electrostatic precipitator
An electrostatic precipitator can remove over 99 percent of particulate matter present in the exhaust from a thermal power plant. It works by charging the dust particles using corona discharge and collecting them on grounded plates.
In an electrostatic precipitator, the velocity of air between the collecting plates must be:
- A Very high to increase collection efficiency
- B Low enough to allow the dust to fall
- C Supersonic to shatter the dust particles
- D Constant and uniform throughout the chamber
Correct answer: Low enough to allow the dust to fall
The velocity of air through the precipitator must be low enough to ensure that the dust particles, once charged and attracted to the collecting plates, actually have time to settle and fall. High velocity would sweep the particles out of the device before they could be collected.
A scrubber is specifically used in industries to remove which of the following gaseous pollutants?
- A Carbon monoxide
- B Nitrogen gas
- C Sulfur dioxide
- D Methane
Correct answer: Sulfur dioxide
In a scrubber, the exhaust is passed through a spray of water or lime. This setup is highly effective at removing gases like sulfur dioxide ($SO_2$) from industrial emissions.
According to the Central Pollution Control Board (CPCB), particulate size of ________ micro-meters or less in diameter are responsible for causing the greatest harm to human health.
- A 5.0
- B 10.0
- C 2.5
- D 1.5
Correct answer: 2.5
Particulate matter of size 2.5 micrometers or less ($PM_{2.5}$) can be inhaled deep into the lungs. These fine particles cause breathing and respiratory symptoms, irritation, inflammations, and premature death.
Catalytic converters, which are fitted into automobiles for reducing emission of poisonous gases, use which of the following expensive metals as catalysts?
- A Iron and steel alloys
- B Platinum-palladium and Rhodium
- C Gold and silver compounds
- D Copper, nickel, and zinc
Correct answer: Platinum-palladium and Rhodium
Catalytic converters use platinum-palladium and rhodium as catalysts to facilitate chemical reactions. These metals help convert unburnt hydrocarbons into CO2 and water, and carbon monoxide and nitric oxide into CO2 and nitrogen gas.
Why is it advised to use unleaded petrol in vehicles fitted with catalytic converters?
- A Lead increases the efficiency of the catalyst
- B Lead in petrol inactivates the catalyst
- C Lead petrol is too expensive for the converter
- D Lead causes the exhaust to freeze
Correct answer: Lead in petrol inactivates the catalyst
Lead in petrol acts as a poison for the precious metal catalysts in the converter. Using leaded petrol neutralizes the platinum, palladium, or rhodium, rendering the device ineffective at reducing pollution.
The Air (Prevention and Control of Pollution) Act was amended in 1987 to include which of the following as an air pollutant?
- A Carbon dioxide
- B Noise
- C Water vapor
- D Dust
Correct answer: Noise
The original Air Act came into force in 1981, but it was amended in 1987. This amendment officially recognized noise as an air pollutant due to its harmful effects on human physiological and psychological health.
Which of the following is a major physiological effect of noise pollution at levels of 150 dB or more?
- A Enhanced and heightened hearing ability
- B Permanent damage to ear drums
- C Increased rate of food digestion
- D Significant reduction in heart rate
Correct answer: Permanent damage to ear drums
Exposure to extremely high sound levels, such as 150 dB generated by a jet plane takeoff, can cause permanent hearing loss. It physically damages the ear drums and the delicate hair cells within the inner ear.
In the 1990s, Delhi ranked ________ among the 41 most polluted cities of the world.
- A First
- B Fourth
- C Tenth
- D Twentieth
Correct answer: Fourth
Due to massive vehicular and industrial growth, Delhi was ranked fourth among the world's most polluted cities in the 1990s. This alarming status led to a Public Interest Litigation (PIL) in the Supreme Court.
Following the Supreme Court's directive, the entire fleet of public transport (buses) in Delhi was switched from diesel to ________ by the end of 2002.
- A Unleaded petrol (ULP)
- B CNG (Compressed Natural Gas)
- C Electric battery systems (EBS)
- D Hydrogen fuel cells (HFC)
Correct answer: CNG (Compressed Natural Gas)
CNG was chosen as a cleaner alternative because it burns more efficiently than diesel or petrol, leaving very little unburnt residue. Additionally, CNG is cheaper and cannot be siphoned off or adulterated easily.
Which of the following is a disadvantage associated with the use of CNG as a fuel for public transport?
- A CNG is more expensive to purchase than diesel
- B CNG produces more sulfur dioxide than conventional fuels
- C Laying pipelines for uninterrupted CNG supply is difficult
- D CNG engines are incompatible with existing vehicle designs
Correct answer: Laying pipelines for uninterrupted CNG supply is difficult
The main challenge with switching to CNG is the logistical difficulty of laying down a vast network of pipelines. This is necessary to ensure a steady, uninterrupted supply to all fueling stations across a large city.
The Euro III norms, which were aimed to control vehicular pollution, specified that sulfur be controlled at ________ in diesel and ________ in petrol.
- A 350 ppm; 150 ppm
- B 50 ppm; 50 ppm
- C 100 ppm; 100 ppm
- D 500 ppm; 250 ppm
Correct answer: 350 ppm; 150 ppm
According to Euro III norms, sulfur content was to be restricted to 350 ppm in diesel and 150 ppm in petrol. The ultimate goal of subsequent norms was to reduce sulfur levels even further to 50 ppm in both fuels.
In India, the Bharat Stage IV (BS IV) emission norms were implemented across the entire country in:
- A April 2010
- B April 2017
- C October 2015
- D January 2020
Correct answer: April 2017
While BS IV was implemented in 13 mega cities in 2010, it was expanded to the entire country in April 2017. Currently, India has skipped BS V and moved directly to BS VI norms to combat rising pollution.
Which plant part is most affected by high concentrations of sulfur dioxide ($SO_2$) in the atmosphere?
- A Root hair cells
- B Xylem and phloem vessels
- C Leaves and chlorophyll
- D Pollen grains and anthers
Correct answer: Leaves and chlorophyll
Sulfur dioxide causes injury to plants by inducing chlorosis (loss of chlorophyll) and necrosis of leaf tissues. This significantly reduces the photosynthetic efficiency and growth of the plant.
What is the function of 'Corona' in an electrostatic precipitator?
- A To cool and filter the incoming air stream
- B To produce a spray of electrons
- C To wash the particulate dust with pressurized water
- D To trap gaseous pollutants chemically
Correct answer: To produce a spray of electrons
The electrostatic precipitator has electrode wires maintained at several thousand volts, which produce a corona that releases electrons. These electrons attach to dust particles, giving them a net negative charge so they can be collected.
Air pollutants affect all living organisms by:
- A Only by reducing growth and yield of crops
- B Only by causing premature death of sensitive plants
- C Only by harming the respiratory system of humans
- D By reducing crops, killing plants, and harming respiration in all living organisms
Correct answer: By reducing crops, killing plants, and harming respiration in all living organisms
Air pollution has multifaceted negative impacts, including reducing agricultural productivity, killing sensitive plant species, and causing severe respiratory and cardiovascular issues in humans and animals.
Which of the following is considered a 'secondary' air pollutant?
- A Carbon monoxide (CO)
- B Tropospheric ozone (O₃)
- C Sulfur dioxide (SO₂)
- D Suspended particulate matter (SPM)
Correct answer: Tropospheric ozone (O₃)
Secondary pollutants are not emitted directly from sources but form in the atmosphere through chemical reactions between primary pollutants and other atmospheric components. Ozone (O₃) is a classic example formed in the presence of sunlight.
A sound level of ________ is considered the threshold for 'noise' that can cause pain or discomfort.
- A 40–50 dB, typical of a quiet library
- B 60–70 dB, the level of normal speech
- C 80–90 dB, loud city traffic noise
- D 120–130 dB, at which physical pain occurs
Correct answer: 120–130 dB, at which physical pain occurs
While constant exposure to 80 dB can cause hearing damage over time, sounds reaching 120–130 dB (like a loud siren or rock concert) reach the threshold of pain for the human ear. Immediate physical discomfort occurs at these levels.
Lichens are well-known 'bio-indicators' because they are extremely sensitive to:
- A Carbon dioxide
- B Sulfur dioxide
- C Nitrogen gas
- D Global warming
Correct answer: Sulfur dioxide
Lichens are highly sensitive to sulfur dioxide pollution and will not grow in areas with high $SO_2$ levels. Their presence or absence is commonly used to assess the air quality of a region.
The use of 'green belts' (planting trees along roadsides) helps in controlling air pollution by:
- A Increasing wind speed
- B Trapping dust and absorbing $CO_2$
- C Reducing the temperature of car engines
- D Producing ozone
Correct answer: Trapping dust and absorbing $CO_2$
Green belts act as natural filters; the leaves trap particulate matter and the trees absorb $CO_2$ while releasing oxygen. They also help in muffle noise pollution from heavy traffic.