2007-02-06 04:55:34 · 13 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Hi Skycat,
Well I once was invited to St. Mary's lighthouse off Northumberland, and was shown that it revolves on a mercury ring bearing arrangement.
The bulbs, three of them, are 1kW each - not a huge lght display, but due to the wonderful circular prismatic arrays, made of stern glass, the whole thing revolved past shutters & windows, to give a distinctive 2-2-1 flash sequence out to sea.
Check the book ...Ah, as in a mariner, you could go " that is St. Marys." Or any other lighthouse. With its' code.
And know, give or take, where you are..
The basis of your Q, I suppose, and the answer to it, is that focus of the light source, heading out is concentratated, and well visible therefore out to sea.
Great big prismatic lenses.
I can't send a diagram via this system, but sort of a concentric series of () () () things.
If I ever meet a female lighthouse keeper, I shall sing :
" Iwant to marry a light-house keeper, and live down by the sea"
According to the Beatles song.
Oh, you can apparently insert coloured filters now.
So if you get a flash of red, offshore - stay away !
All the best to the folks that operate lighthouses.
My praise to them.
Cheers,
Bob the Boat
2007-02-06 05:25:31 · answer #1 · answered by Bob the Boat 6 · 1⤊ 0⤋
First you need a really bright light.
Second, you use two very large lenses to focus the light that would normally spread in all directions in just two directions, on either side of the lighthouse. The lens is a little bit like a magnifier glass, but a lot larger. The net result is that the light intensity is focused in two directions.
By having these two large lenses rolling on circular rails, the focused light beams point all around the lighthouse as they turn, to cover all directions. This is why the lighthouse appears to flash when you are at sea: the focused light only points at you while the lenses point in your direction.
The lens is so big (6 feet or more) that they actually use Fresnel lenses, that are thinner but have the same shape. Otherwise, the lighthouse lenses would be so big it would be hard to raise them on top of the lighthouse, and turning them would require a lot of energy.
2007-02-06 05:12:10 · answer #2 · answered by The Goal Interceptor 2 · 1⤊ 0⤋
The light is not magnified as much as it is concentrated. The light source is backed by a reflector to send more light out in the desired direction. The light itself is focussed by a fresnel lens, which has circular steps resulting in a similar effect to an much larger unstepped lens.
2007-02-06 05:05:12 · answer #3 · answered by Dan in Boston 4 · 1⤊ 0⤋
Its actually really simple, the light is actually surrounded by a huge glass prism which magnifies it and directs it as a beam out to sea.
2007-02-06 04:59:41 · answer #4 · answered by Need2know 3 · 1⤊ 0⤋
This puzzle seems exciting yet light fixtures speed is a unique quantity say three hundred,000km/sec. think you get carry of a mild from a source that is transferring quick remote from you,then mild will under no circumstances attain you. also a source that is coming in the route of then you, % of light ought to change and may attain you earlier.this does no longer happen. you may analyze this in relativity . the speed of light is consistent climate the source strikes or the observer strikes.
2016-11-25 20:22:56 · answer #5 · answered by rensing 4 · 0⤊ 0⤋
The ligt is amplified by a Fresnel Lens. Check the link.
2007-02-06 05:07:45 · answer #6 · answered by gleemonex69 3 · 1⤊ 0⤋
A fresnel lens is used
2007-02-06 05:03:36 · answer #7 · answered by David P 7 · 2⤊ 0⤋
t has many spotless mirrors for the lamp to be reflected.
2007-02-06 05:15:47 · answer #8 · answered by DIAMOND_GEEZER_56 4 · 1⤊ 0⤋
with a huge lens
2007-02-06 05:23:31 · answer #9 · answered by rosie recipe 7 · 1⤊ 0⤋
shaped mirrors
2007-02-06 04:58:22 · answer #10 · answered by Anonymous · 1⤊ 0⤋