Question 25Navigation 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 40 feet (12.2 meters) and the visibility is 27.0 miles. At which approximate range will you first sight the light?

A 5.6 miles
B 6.4 miles
C 9.8 miles
D 12.1 miles
AI Explanation

The correct answer is C) 9.8 miles. The range at which you will first sight the navigational light can be calculated using the formula for geographical range, which takes into account the height of the light and the height of the observer's eye. The formula is: Geographical Range (in nautical miles) = 2.076 * (sqrt(height of light in feet) + sqrt(height of eye in feet)). Plugging in the given values, we get: 2.076 * (sqrt(18) + sqrt(40)) = 2.076 * (4.24 + 6.32) = 9.8 miles. The other options are incorrect because they do not properly account for the height of the light and the height of the observer's eye in the geographical range calculation.

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