The Fresnel Lens

This drawing shows the Fresnel lens and light source used in the Point Moore Lighthouse. Invented in 1822 by French physicist Augustin-Jean Fresnel, this ingenious design places the light source inside a rotating cage of lenses and prisms, known as an optic, which bends and reflects light into a powerful, focused beam.

Lighthouse lenses are grouped into six “orders” based on focal distance, the measurement from the light source to the central bullseye lens. A greater focal distance produces a stronger beam: a first-order lens reaches 920 mm, while a sixth-order lens is only 150 mm. The Point Moore lens is a second-order lens with a focal distance of 700 mm, producing a beam visible from 19 nautical miles away.

By combining precision engineering with the height of the tower and the curve of the Earth, the Fresnel lens guided countless ships safely to the Geraldton coast.