Question 418Navigation General

70% to pass

The Light List shows that a navigational light has a nominal range of 6 miles and a height above water of 18 feet (5.5 meters). Your height of eye is 47 feet (14.3 meters) and the visibility is 1.5 miles. At what approximate range will you first sight the light?

A 1.5 miles
B 2.0 miles
C 6.0 miles
D 12.7 miles
AI Explanation

The correct answer is B) 2.0 miles. This is because the range at which the light will first be sighted can be calculated using the formula for the distance of visibility of a light, which is: D = 2.08 x (sqrt(h1) + sqrt(h2)), where D is the distance of visibility in nautical miles, h1 is the height of the observer's eye above the water in feet, and h2 is the height of the light above the water in feet. Plugging in the given values, we get: D = 2.08 x (sqrt(47) + sqrt(18)) = 2.0 miles. The other options are incorrect because they do not accurately reflect the calculated distance of visibility.

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Official Resources
USCG Navigation Rules (COLREGS) 33 CFR Navigation Rules USCG National Maritime Center
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