🔍 Key Concepts

• Geographic range of a light (how far it can be seen based on height and earth’s curvature) • Luminous range of a light (how far it can be seen based on intensity and visibility conditions) • What information about lights is shown on a nautical chart and in the Light List

💭 Think About

• Ask yourself: when cartographers decide what to print on the chart for a lighthouse, are they concerned with the observer’s actual eye height, or with fixed characteristics of the aid to navigation itself? • Consider which of the listed factors change from vessel to vessel and which are constant for all mariners looking at the same charted light. • Think about which factor determines how bright the light appears in clear weather versus which factor determines whether the earth’s curvature hides the light.

✅ Before You Answer

• Identify which options involve only properties of the light itself versus properties of the mariner or vessel. • Recall that charts often show a light’s nominal range and its elevation (height above mean high water)—verify which answer choice best matches those charted items. • Eliminate any choice that depends on who is looking at the light, since charts must be valid for all observers.