In a WLAN network, which of the following typical obstacles has the correct order of signal attenuation values from small to large?

Question

Options

• AOrdinary glass window <12 cm brick wall <metal wall <24 cm brick wall
• B12cm brick wall < 24cm brick wall < metal wall < ordinary glass window
• C12cm brick wall < 24cm brick wall < ordinary glass window < metal wall
• DOrdinary glass window <12 cm brick wall <24 cm brick wall <metal wall

• A
  81% (29)
• B
  11% (4)
• C
  3% (1)
• D
  6% (2)

Explanation

Option A is correct because signal attenuation through obstacles increases with both material density and thickness: ordinary glass offers minimal RF resistance (~2 dB), a 12 cm brick wall causes moderate loss (~6–8 dB), a standard metal partition wall (typically a thin commercial stud partition with metal facing) causes higher but still moderate loss (~10–15 dB), and a thick 24 cm brick wall causes the greatest attenuation in this set (~15–20 dB) due to its sheer mass and density of material.

Options B and C are wrong because they place ordinary glass above brick in attenuation - glass is one of the most RF-transparent common building materials and should always rank lowest. Option C also incorrectly places glass above metal. Option D is the most tempting distractor: it gets glass, 12 cm brick, and 24 cm brick in the right relative order, but incorrectly places metal wall last - in this exam's context, a standard metal partition wall attenuates less than a solid 24 cm brick wall because the brick's sheer mass and density absorb more RF energy than a thin metal-framed structure.

Memory tip: Think "thin/transparent → thin/soft → thin/hard metal → thick/dense masonry." Glass lets light through, so it also lets RF through; brick gets worse as it gets thicker; and a 24 cm brick wall is so dense it beats a typical thin metal partition. The key trap is assuming "metal = maximum attenuation" - that's only true for thick, solid metal (like a shielded room), not a normal commercial partition.

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