The Light List shows that a navigational...

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Question 1 of 2066636ee928f7522a1c519aaa

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?

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Question 1 of 20

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🔍 Key Concepts

• Geographic range vs. luminous (nominal) range of a light • How to compute distance to the horizon from height of eye and light height • Effect of meteorological visibility on the visible range of a light

💭 Think About

• First, figure out how far away the light could be seen just from curvature of the earth using the heights given. Is that distance more or less than the choices? • Next, compare the nominal range with the visibility given. How does reduced visibility affect how far away a light can actually be seen? • Which factor will limit you first in this problem: the earth’s curvature (geographic range) or the brightness/visibility (luminous range)?

✅ Before You Answer

• Use the standard distance-to-horizon formula for both the light and your eye height, then add them to get geographic range. • Compare your computed geographic range with the nominal range (19 miles) and the 10-mile visibility to see which is the controlling limit. • Eliminate any answer choices that are greater than both the distance allowed by visibility and the distance to the horizon.

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