A bag filter is used for removal of particulate matter having a range of sizes. The correct sequence of air filtration mechanisms for their removal, in order of decreasing size, is
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- Diffusion, Impaction, Disintegration
- Disintegration, Impaction, Interception
- Diffusion, Impaction, Interception
- Impaction, Interception, Diffusion
The Correct Option is A
Solution and Explanation
Step 1: Understand filtration mechanisms by particle size.
Impaction removes large particles (coarse PM) because they cannot follow air streamlines and impact directly onto filter fibers.
Interception removes medium-size particles that follow streamlines but touch fibers and get captured.
Diffusion removes the smallest particles (PM$_{2.5}$, ultrafine) due to Brownian motion.
Step 2: Arrange from largest to smallest particle size.
Largest particles → Impaction
Medium particles → Interception
Smallest particles → Diffusion
Thus the correct decreasing size sequence is: \[ \boxed{\text{Impaction} ;>; \text{Interception} ;>; \text{Diffusion}} \] This corresponds to option (D).
Final Answer: (D)
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