🔍 Key Concepts

• Geographic range vs. luminous (nominal) range of a light • Formula for geographic range based on height of eye and height of light (sum of distances) • Effect of meteorological visibility on the nominal range of a light (conversion to a reduced luminous range)

💭 Think About

• First, think about how to find how far away the light could be seen just from the heights involved (your eye height plus the light height). What standard formula or table is used for that? • Next, consider that the light’s nominal range is given for a standard visibility of 10 miles. How does actual visibility of 11 miles change that luminous range? Would it increase or decrease it, and roughly by how much? • Finally, compare the geographic range you found with the visibility-limited (luminous) range. Which one actually limits when you first see the light, and which answer choice is closest to that limiting range?

✅ Before You Answer

• Make sure you convert heights in feet to distance in nautical miles using the proper geographic range formula or table (one distance for the light, one for your eye, then add). • Verify whether nominal range 18 miles is or is not reduced by the 11‑mile meteorological visibility using the luminous range diagram concept (even if you estimate it mentally). • Before picking an answer, decide clearly which is smaller: the geographic range or the visibility-limited luminous range—that smaller distance is the one that controls when you first see the light.