Through a different kind of lens

Using waterdrop art to explain optics

I am a huge fan of the art of photography. I love how some people are able to catch the perfect moment at the perfect time and place and just get it right with their camera. And sometimes, things can turn out pretty science-y. And when you think about it, it’s pretty obvious how photography is a lot of optical physics. Let me show you what I mean.

A couple of months back, I wrote a guest post for my friend Mirjam on a physics magic trick with two arrows and a glass of water. I really loved how easy the experiment was and that it was so powerful in explaining how water sometimes acts as lenses. And then I stumbled across this picture:

The flower is obviously turned uside down by the water drop.
Found at https://bit.ly/2LB5ZuH .

Isn’t it amazing how the flower seems to be upside down when looking through the water drops? I tried to replicate the picture with a little modified surroundings.

In the water droplets, the arrow is turned upside down as well.

The physics behind these pictures is rather simple. The water acts like a lens, because refraction of light is different in water than it is in air. Since the water drops are shaped like little balls, they behave like positive (converging) lenses. With the water drops being so tiny and the object so much larger, it does not have the magnifying effect like in my post for Mirjam. Nonetheless, it works the same.

The real image of the arrow (the one we see with out eyes or with the camera of my phone), is upside down and smaller than the original arrow. An illustration of the light way can be found here:

Lens3.svg
By w:en:DrBobw:en:File:Lens3.svg, GFDL, Link

Now I usually include some instructions for those of you who might want to reproduce the experiment. And this one was quite fun, although a little tricky to capture. I used an old photo frame and cleaned the glass, stacked it between two waterglasses and carefully dripped some water on top. There are tons of great pictures out there with sweets or flowers under the glass but the most important thing is to keep your eyes focused on the water droplets (same goes for a camera if you want to take a picture). Have fun!

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