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Navigation lights and shapesQuestion 72 of 352

How wide is the arc of a masthead light?

  1. 112.5 degrees
  2. 135 degrees
  3. 360 degrees
  4. 225 degrees
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Correct answer: 225 degrees

A masthead light shines over 225 degrees, from straight ahead to 22.5 degrees behind the beam on each side.

Source: US Code of Federal Regulations (eCFR), 33 CFR Part 83: Inland Navigation Rules, § 83.21 Definitions (Rule 21)

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Questions last reviewed: 18 October 2026