Parabolic Reflector


How lighthouses work

How lighthouses work
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A Lighthouse, in the broadest terms, is a fully or partially enclosed, built structure bearing a light that is used as a navigational aid and that is capable of admitting at least one person to operate or maintain the light entirely from within.

A Little Lighthouse History

  • Lighthouses have been around for a long time, most certainly longer than recorded history can tell us about. The famous Lighthouse at Alexandria, one of the Seven Wonders of the Ancient World, is the oldest one cited by many classical writers and historians. Dating from sometime between 323 and 270 B.C., it is improbable that is had no antecedents. The Pharaoh Ptolemy would hardly have put the huge resources need to built this edifice if it had no proven track record.
  • The Alexandria lighthouse was called “Pharos”. Either that was the name of the tiny island on which it was built or that is what the island came to be called after the lighthouse was built. No one knows for sure. But the word comes down to us in modern languages: faro (Spanish), phare (French), faro (Italian), farol (Portuguese), far (Romanian).

Beacons and Hilltop Fires

  • Lindesnes

    The earliest lighthouses were simply bonfires built on hillsides to guide ships. Ancient peoples had long made a practice of banking fires on hills and mountainsides to bring their sailors home from the sea.

  • Ryvarden Lighthouse is the site of a stone fireplace built in 869 by the viking Floke Vilgerdson (aka Ramnaflok). The cairn that Floke built before he left was later given the name Ryvarden (Rycairn), and is probably the oldest cairn along the coast.
  • First lit in 1655, Lindesnes Lighthouse is Norway’s oldest lighthouse. Ever since the Middle Ages, Lindesnes, or “headland”, as the spot was called, has been one of the most important naviagation landmarks for boats for sailing between the North and Baltic Seas.

Light Sources

  • To be effective, lights had to be continuous and uninterrupted. The keepers were kept very busy during their period of duty, ensuring a constant supply of fuel to the light and keeping everything clean and in good working order.
  • Wood. There are few definite instances of lighthouses being fed by wood fires, although they would have no doubt been used in crude beacons on headlands, for instance
  • Coal. For centuries coal was used to feul. The effort to get the coal to the lighthouse and up to the light was not insignificant. Villa Lighthouse, built in 1839, was one of  six coal-fired lighthouses built in Norway and was perhaps the last built in the world. It was converted to burn liquid fuels in 1859.
  • Vaporized Paraffin and Acetylene. Both used for many years. Acetylene is today chiefly used in buoys and other automated systems.
  • Electric Light Bulbs. large incandescent light bulbs have been used for many decades of the 20th century and still are in many lighthouses. Today, solar power and LEDs  are coming more and more into play at lighthouses.

Making a Strong Light

  • Parabolic Reflector

    An effective light has to be seen well before the danger is encountered.

  • Parabolic reflectors were found to strengthen the lightbeam. Ligth sources emit light is all directions. These reflectors redirect light in the desired direction making it much stronger and able to be seen at greater distances.
  • Fresnel Lenses. In 1822, Augustin Fresnel perfected a lens system that was to revolutionize the entire design and construction of lighthouse optics. He created a structure made of lenses and prisms that looked like a giant bee-hive of glass. this complex combination collected all rays of light emanating from a light source at the centre of the optic and produced a bright narrow sheet of light from its center. A first order optic is very large, produciund a bright powerful light and is intended for use in the most strategic locations on the coast. A sixth order optic is smallest and is intended for harbors.

Types of Lighthouses in Norway

  • Coastal lighthouses (Kystfyrene located towards the sea and ships’ first landfall. They often are taller lighthouse located on islands  and headlands. These are very strong lights because they will be clearly visible at long distances.
  • Approach lighthouses (Innseilingsfyrene) lead shipping safely to the shore.
  • Guiding lighthouses (Ledfyreneare smaller lighthouses showing lanes in the inner coastal waters between the islands and the approach to narrow strait. They emit light signals at specified intervals and in certain directions or sectors. This is therefore also called sektorfyr.
  • Port Lighthouses (Havnefyrene) help ships into the harbor.
Fishing lighthouses (Fiskefyr) used during the fishing season in Norway. These work-specific lighthouse arose in Norway after 1850.
  • Lightships (Fyrskip or fyrlykter) are beacons placed on permanently anchored vessel where it is unsuitable to build permanent fire. Light-vessels had only minor distribution in Norway.



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