revolving-beam lighthouse

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 13, 2026

Quick Summary

A revolving-beam lighthouse uses a rotating optical apparatus, typically a mirror or lens, to concentrate and project a light source into a beam. This beam sweeps across the horizon, creating a flashing effect that allows mariners to identify the lighthouse from any direction. The first practical mirrors for lighthouses were developed in 1777, and the first revolving-beam lighthouse was established in 1781 in Sweden. While initially met with some resistance from mariners who preferred a steady light, the increased intensity and the ability to use unique flash patterns for identification eventually led to their widespread adoption.1

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

lighthouse
Paraboloidal mirrors
This produced the now familiar revolving lighthouse beam, with the light appearing as a series of flashes. Mariners were not favorably disposed to these early flashing lights, contending that a fixed steady light was essential for a satisfactory bearing. However, the greatly increased intensity and the advantage of using a…
Read More
This produced the now familiar revolving lighthouse beam, with the light appearing as a series of flashes. Mariners were not favorably disposed to these early flashing lights, contending that a fixed steady light was essential for a satisfactory bearing. However, the greatly increased intensity and the advantage of using a…
Read More