Schlieren photography

Have you ever seen movies or TV shows that show invisible air moving around objects, like in the cartoons? Schlieren photography can show us something like that in real life!

Schlieren photography is a super cool way to take pictures of tiny changes in the air around objects. We can't usually see these changes with our eyes, but schlieren photography lets us capture the changes visually.

Here's how it works: first, we take a picture of a plain background, like a white wall, without any objects in it. Then, we set up a light source, like a candle or an LED, to shine light through the air. We put the object we want to photograph in between the light source and the plain background. We use mirrors to bounce the light around at an angle.

Now, here's where it gets a bit tricky: when light moves through air, it sometimes changes direction a tiny bit. In the schlieren photography setup, we can use this fact to our advantage. By adjusting the mirrors just so, we can make the light that's moving through the air around the object move in a slightly different direction than the light that hasn't moved through that air.

We use a special schlieren lens in the camera to capture this difference. The lens has a curved edge that bends the incoming light in different directions depending on how it has been affected by the air around the object. Then, we take another picture of the plain background, this time with the light source turned off.

When we compare the two pictures, we can see the changes in the air around the object! Usually, the changes show up as dark or light areas surrounding the object, like a cloudy halo. This happens because the changes in the air affect how much light the schlieren lens captures.

Schlieren photography can help us understand how air flows when we move through it or when things move past us. Scientists use it to study how planes move through the air or how rockets launch into space. It's a really neat way to take pictures of things that our eyes can't usually see!