On a SHOA nautical chart, the elevation of a lighthouse structure is stated as 49 meters above Mean High Water Springs. What optical/geometric factor defines its 'geographic range' (alcance geográfico) as seen from the bridge of a small craft?

1. The curvature of the Earth combined with the height of the light and the observer's eye height above sea level
2. The electrical wattage and luminous intensity of the light bulb alone
3. The atmospheric visibility coefficient under dense fog conditions
4. The magnetic variation of the local geographic zone