🔍 Key Concepts

• Existing visibility vs. standard conditions for lights • Difference between charted/nominal data and what you actually see at sea • How luminous intensity and geographic factors (height of eye, curvature of the earth) affect ranges

💭 Think About

• Which of these terms depends on the current weather and visibility, and which are fixed values printed on charts or in light lists? • Think about a foggy night: which term describes how far you can actually see the light right now, versus how far it could be seen under standard conditions? • Which term is based on the light’s brightness alone, and which one involves the observer’s height of eye and the light’s height? Identify which best matches the phrase ‘under existing visibility conditions.’

✅ Before You Answer

• Identify which options are purely chart values that don’t change with weather or visibility. • Separate terms that relate to light intensity from those that relate to earth curvature and height of eye. • Match the definition carefully: look for the one that explicitly ties to present visibility conditions, not clear-weather or standard conditions.