H12-311_V3.0 · Question #187
20dBm is equivalent to () mW.
The correct answer is A. 100. 20 dBm = 100 mW (Option A) because the conversion formula is P(mW) = 10^(dBm/10), so 10^(20/10) = 10² = 100 mW. Options B (200 mW), C (500 mW), and D (1000 mW) are incorrect - 1000 mW would actually be 30 dBm, making D the most common trap since test-takers sometimes confuse…
Question
20dBm is equivalent to () mW.
Options
- A100
- B200
- C500
- D1000
How the community answered
(34 responses)- A82% (28)
- B3% (1)
- C6% (2)
- D9% (3)
Explanation
20 dBm = 100 mW (Option A) because the conversion formula is P(mW) = 10^(dBm/10), so 10^(20/10) = 10² = 100 mW. Options B (200 mW), C (500 mW), and D (1000 mW) are incorrect - 1000 mW would actually be 30 dBm, making D the most common trap since test-takers sometimes confuse the factor-of-10 dB rule (every +10 dB = ×10 power) with starting from 1 mW (0 dBm) rather than applying it correctly. B and C have no clean dBm equivalents and serve as plausible-looking distractors.
Memory tip: Use the "10/3 rule" - every +10 dBm multiplies power by 10, and every +3 dBm roughly doubles it. Starting from 0 dBm = 1 mW: +10 dBm → 10 mW, +20 dBm → 100 mW, +30 dBm → 1000 mW. So 20 dBm lands squarely at 100 mW.
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