The GATE Grind

GATE 2026 ES – Question 21

Air and Noise Pollution · Particulate Pollutants · 1 mark · Multiple choice

In air pollution control device design, the size of particles removed with 50% efficiency is called

  1. Mean size
  2. Mode size
  3. Cut size
  4. Median size

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Show answer and explanation

Correct answer: (C) Cut size

Explanation

A device’s grade-efficiency curve gives removal efficiency against particle size. The diameter at 50% collection is its cut size, often denoted $d_{50}$. Mean, mode and median describe particle-size distributions and do not by themselves specify collection efficiency. Hence **C**.

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