Tag Archives: lense

Lighthouses and Fresnel lenses

Or more reasons for why I want to live in a lighthouse.

I have always been fascinated by lighthouses. Always. Usually because they are built in the most wonderful places and I would just love to live there. For example one near San Francisco that has this view:


Golden Gate Bridge

But then also because they can cast their beams of light over such long distances, even though they look perfectly harmless during daytime:


Close-up of the same lighthouse as above

So this is what the inside looks like (pictures taken at the ThinkTank science museum in Birmingham, UK):


The insides of a lighthouse

And the whole thing is only lit by a tiny lightbulb!


And there is just a tiny light bulb on the inside!

Watch the movie below to see how the light is focused by the Fresnel lenses. Really fascinated how the light bulb is surrounded only by glass, but still the light is focused really sharply.

I have a Fresnel lense that I’ll play around with soon, so stay tuned for more on cool optics! :-)

Refraction of light in water – coins and lenses.

More on what water can do to light.

Remember my fascination with dandelions? Just to remind you:



Especially in combination with coins and water droplets, dandelions are a source of nearly endless entertainment:


1 NOK with water droplet in the hole in the middle.

See how much cooler 1 NOK coins become only by adding a little water?


The upper coin does not have water in the hole, the lower one does. See the difference?

Here the same two coins in the sun – see how the water droplet in the coin in the back focusses the light whereas the empty hole in the coin in the front is just a hole?


The coin in the foreground doesn’t have water in the hole, the one in the back does. See how they affect light differently?

Pretty cool stuff. And in the next post I’ll show you what this very effect does out in the real world!


Left coin without water, right coin with water in the hole in the middle.