Environmental Issues — NEET UG practice

1. Recall what an electrostatic precipitator (ESP) does: An ESP is a device that removes particulate matter (like dust and soot) from the exhaust gases of thermal power plants, using electrically charged plates that attract and trap the charged dust particles.

2. Evaluate Statement I: Since ESPs are indeed the most common and effective device installed in thermal power plants to control particulate air pollution, Statement I is correct.

3. Evaluate Statement II: The purpose of an ESP is to remove suspended solid particles from smoke, not to remove ionising radiations (which are a completely different physical phenomenon related to radioactive decay or high-energy radiation, not solid pollutants). So Statement II is incorrect.

4. Conclude: Statement I is true while Statement II is false.

Hence, the answer is B. Statement I is correct but Statement II is incorrect.

1. Recall the relationship between BOD and dissolved oxygen: BOD (Biochemical Oxygen Demand) measures how much oxygen microorganisms consume while decomposing organic matter. The more organic matter present, the more oxygen bacteria use up, so BOD and dissolved oxygen move in opposite directions.

2. Evaluate statement (A): Since more organic matter means higher BOD and lower dissolved oxygen, BOD is indeed inversely related to dissolved oxygen. Statement (A) is correct.

3. Evaluate statement (B): When dissolved oxygen is low and BOD is high, aquatic organisms like fish cannot get enough oxygen to survive, resulting in loss of aquatic life. Statement (B) is correct.

4. Evaluate statement (C): Since BOD and dissolved oxygen are inversely related (from step 1), high BOD actually causes low, not high, dissolved oxygen. Statement (C) is incorrect.

5. Evaluate statement (D): Because both measures reflect the amount of organic pollution and oxygen availability, they are commonly used together as indicators of the health of a water body. Statement (D) is correct.

6. Evaluate statement (E): More organic matter increases the oxygen demand (raising BOD) while simultaneously lowering dissolved oxygen — so both parameters are affected by the amount of organic matter. Statement (E) is correct.

7. Combine the correct statements: (A), (B), (D), and (E) are correct, while (C) is false.

Hence, the answer is B. (A), (B), (D), (E) only.

1. Understand what is being measured: The ozone layer is not uniformly thick everywhere; its concentration in a vertical column of air (from the ground up to the top of the atmosphere) needs a special unit for measurement.

2. Identify the correct unit: This thickness is measured using Dobson units (DU), where one Dobson unit corresponds to a very thin layer of ozone gas if compressed to standard temperature and pressure.

3. Rule out the other options: Decibels measure sound intensity/noise, not ozone thickness; decameter is simply a unit of length (10 meters) with no special connection to ozone; kilobase is a unit used to measure the length of DNA or RNA sequences, unrelated to atmospheric gases.

Hence, the answer is D. Dobson units.