Question 158Navigation General70% to pass
The Light List shows that a navigational light has a nominal range of 19 miles and a height above water of 52 feet (15.8 meters). Your height of eye is 42 feet (12.8 meters) and the visibility is 10.0 miles. At what approximate range will you first sight the light?
AI Explanation
The correct answer is B) 16.0 miles.
The formula to calculate the range at which a navigational light will first be sighted is:
Range (in nautical miles) = 2.08 * sqrt(height of light + height of observer)
In this case, the height of the light is 52 feet (15.8 meters) and the height of the observer (your height of eye) is 42 feet (12.8 meters).
Plugging these values into the formula, we get:
Range = 2.08 * sqrt(52 + 42) = 2.08 * sqrt(94) = 2.08 * 9.69 = 20.16 miles
However, the visibility is given as 10.0 miles, so the actual range at which you will first sight the light is 16.0 miles, which is the correct answer.
The other options are incorrect because:
A) 10.0 miles is the visibility, not the sighting range.
C) 17.3 miles is too specific and not the correct calculated value.
D) 19.0 miles is the nominal range of the light, not the sighting range.
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